Kinda big, but I did it in two different imports
First deleted all orders and customers with the queries in this question https://github.com/magento/data-migration-tool/issues/467#issuecomment-627912182
Then do a map.xml, this might depend on your tables, I had to ignore extensions tables and other ones, was a trial error, backup your database and try, if something is wrong go back and check where it is on database then add that table to ignore, in that last answer on git a posted a bit but too much lines to post it here.
To import customers
<?xml version="1.0" encoding="UTF-8"?>
<steps mode="data">
<!-- <step title="Data Integrity Step">
<integrity>Migration\Step\DataIntegrity\Integrity</integrity>
</step>
<step title="EAV Step">
<integrity>Migration\Step\Eav\Integrity</integrity>
<data>Migration\Step\Eav\Data</data>
<volume>Migration\Step\Eav\Volume</volume>
</step> -->
<step title="Customer Attributes Step">
<integrity>Migration\Step\Customer\Integrity</integrity>
<data>Migration\Step\Customer\Data</data>
<volume>Migration\Step\Customer\Volume</volume>
</step>
<!-- <step title="Map Step">
<integrity>Migration\Step\Map\Integrity</integrity>
<data>Migration\Step\Map\Data</data>
<volume>Migration\Step\Map\Volume</volume>
</step>
<step title="Url Rewrite Step">
<integrity>Migration\Step\UrlRewrite\Version191to2000</integrity>
<data>Migration\Step\UrlRewrite\Version191to2000</data>
<volume>Migration\Step\UrlRewrite\Version191to2000</volume>
</step> -->
<!-- <step title="Log Step">
<integrity>Migration\Step\Log\Integrity</integrity>
<data>Migration\Step\Log\Data</data>
<volume>Migration\Step\Log\Volume</volume>
</step> -->
<!-- <step title="Ratings Step">
<integrity>Migration\Step\Ratings\Integrity</integrity>
<data>Migration\Step\Ratings\Data</data>
<volume>Migration\Step\Ratings\Volume</volume>
</step>
<step title="ConfigurablePrices step">
<integrity>Migration\Step\ConfigurablePrices\Integrity</integrity>
<data>Migration\Step\ConfigurablePrices\Data</data>
<volume>Migration\Step\ConfigurablePrices\Volume</volume>
</step> -->
<!-- <step title="OrderGrids Step">
<integrity>Migration\Step\OrderGrids\Integrity</integrity>
<data>Migration\Step\OrderGrids\Data</data>
<volume>Migration\Step\OrderGrids\Volume</volume>
</step>
<step title="Tier Price Step">
<integrity>Migration\Step\TierPrice\Integrity</integrity>
<data>Migration\Step\TierPrice\Data</data>
<volume>Migration\Step\TierPrice\Volume</volume>
</step>
<step title="SalesIncrement Step">
<integrity>Migration\Step\SalesIncrement\Integrity</integrity>
<data>Migration\Step\SalesIncrement\Data</data>
<volume>Migration\Step\SalesIncrement\Volume</volume>
</step>
<step title="PostProcessing Step">
<data>Migration\Step\PostProcessing\Data</data>
</step>-->
</steps>
<steps mode="delta">
<step title="Customer Attributes Step">
<delta>Migration\Step\Customer\Delta</delta>
<volume>Migration\Step\Customer\Volume</volume>
</step>
</steps>
<source>
<database host="xxxxxxx" name="database_name" user="user" password="password"/>
</source>
<destination>
<database host="xxxxxxx" name="database_name" user="user" password="password"/>
</destination>
<options>
<map_file>etc/opensource-to-opensource/1.9.0.1/map.xml.dist</map_file>
<eav_map_file>etc/opensource-to-opensource/map-eav.xml.dist</eav_map_file>
<eav_document_groups_file>etc/opensource-to-opensource/eav-document-groups.xml.dist</eav_document_groups_file>
<eav_attribute_groups_file>etc/opensource-to-opensource/eav-attribute-groups.xml.dist</eav_attribute_groups_file>
<log_map_file>etc/opensource-to-opensource/map-log.xml.dist</log_map_file>
<log_document_groups_file>etc/opensource-to-opensource/log-document-groups.xml.dist</log_document_groups_file>
<settings_map_file>etc/opensource-to-opensource/settings.xml.dist</settings_map_file>
<customer_map_file>etc/opensource-to-opensource/map-customer.xml.dist</customer_map_file>
<customer_document_groups_file>etc/opensource-to-opensource/customer-document-groups.xml.dist</customer_document_groups_file>
<customer_attribute_groups_file>etc/opensource-to-opensource/customer-attribute-groups.xml.dist</customer_attribute_groups_file>
<delta_document_groups_file>etc/opensource-to-opensource/deltalog.xml.dist</delta_document_groups_file>
<order_grids_document_groups_file>etc/opensource-to-opensource/order-grids-document-groups.xml.dist</order_grids_document_groups_file>
<map_document_groups>etc/opensource-to-opensource/map-document-groups.xml.dist</map_document_groups>
<class_map>etc/opensource-to-opensource/class-map.xml.dist</class_map>
<tier_price_map_file>etc/opensource-to-opensource/map-tier-price.xml.dist</tier_price_map_file>
<stores_map_file>etc/opensource-to-opensource/map-stores.xml.dist</stores_map_file>
<!--
In case bulk_size=0 it will be auto-detected for every document.
-->
<bulk_size>0</bulk_size>
<!--
Set direct_document_copy = 1 for better performance.
NOTE: 'source' and 'destination' databases MUST be placed on the same MySQL instance
and 'destination' user MUST be granted with 'SELECT' permissions on 'source' database
-->
<direct_document_copy>0</direct_document_copy>
<source_prefix />
<dest_prefix>pe</dest_prefix>
<auto_resolve_urlrewrite_duplicates>0</auto_resolve_urlrewrite_duplicates>
<log_file>migration.log</log_file>
<progress_bar_format>%percent%% [%bar%] Remaining Time: %remaining%</progress_bar_format>
<upgrade_customer_password_hash>1</upgrade_customer_password_hash>
<edition_migrate>opensource-to-opensource</edition_migrate>
<edition_number>1.9.0.1</edition_number>
<init_statements_source>SET NAMES utf8;</init_statements_source>
<init_statements_destination>SET NAMES utf8;</init_statements_destination>
<crypt_key>04a54072077cb6e32e54dee19b47cc3f</crypt_key>
</options>
After this, if you can't login with a customer account truncate customer_entity_varchar, it's caused by a change in hash I think so truncate so it's regenerated and all good.
then, orders
<?xml version="1.0" encoding="UTF-8"?>
<!--
/**
* Copyright © Magento, Inc. All rights reserved.
* See COPYING.txt for license details.
*/
-->
<config xmlns:xs="http://www.w3.org/2001/XMLSchema-instance" xs:noNamespaceSchemaLocation="../../config.xsd">
<steps mode="data">
<!-- <step title="Data Integrity Step">
<integrity>Migration\Step\DataIntegrity\Integrity</integrity>
</step>
<step title="EAV Step">
<integrity>Migration\Step\Eav\Integrity</integrity>
<data>Migration\Step\Eav\Data</data>
<volume>Migration\Step\Eav\Volume</volume>
</step>
<step title="Customer Attributes Step">
<integrity>Migration\Step\Customer\Integrity</integrity>
<data>Migration\Step\Customer\Data</data>
<volume>Migration\Step\Customer\Volume</volume>
</step>-->
<step title="Map Step">
<integrity>Migration\Step\Map\Integrity</integrity>
<data>Migration\Step\Map\Data</data>
<volume>Migration\Step\Map\Volume</volume>
</step>
<!--<step title="Url Rewrite Step">
<integrity>Migration\Step\UrlRewrite\Version191to2000</integrity>
<data>Migration\Step\UrlRewrite\Version191to2000</Imdata>
<volume>Migration\Step\UrlRewrite\Version191to2000</volume>
</step>
<step title="Log Step">
<integrity>Migration\Step\Log\Integrity</integrity>
<data>Migration\Step\Log\Data</data>
<volume>Migration\Step\Log\Volume</volume>
</step>
<step title="Ratings Step">
<integrity>Migration\Step\Ratings\Integrity</integrity>
<data>Migration\Step\Ratings\Data</data>
<volume>Migration\Step\Ratings\Volume</volume>
</step>
<step title="ConfigurablePrices step">
<integrity>Migration\Step\ConfigurablePrices\Integrity</integrity>
<data>Migration\Step\ConfigurablePrices\Data</data>
<volume>Migration\Step\ConfigurablePrices\Volume</volume>
</step> -->
<step title="OrderGrids Step">
<integrity>Migration\Step\OrderGrids\Integrity</integrity>
<data>Migration\Step\OrderGrids\Data</data>
<volume>Migration\Step\OrderGrids\Volume</volume>
</step>
<!-- <step title="Tier Price Step">
<integrity>Migration\Step\TierPrice\Integrity</integrity>
<data>Migration\Step\TierPrice\Data</data>
<volume>Migration\Step\TierPrice\Volume</volume>
</step> -->
<step title="SalesIncrement Step">
<integrity>Migration\Step\SalesIncrement\Integrity</integrity>
<data>Migration\Step\SalesIncrement\Data</data>
<volume>Migration\Step\SalesIncrement\Volume</volume>
</step>
<!--<step title="PostProcessing Step">
<data>Migration\Step\PostProcessing\Data</data>
</step>-->
</steps>
<steps mode="delta">
<step title="SalesIncrement Step">
<delta>Migration\Step\SalesIncrement\Delta</delta>
<volume>Migration\Step\SalesIncrement\Volume</volume>
</step>
<step title="OrderGrids Step">
<delta>Migration\Step\OrderGrids\Delta</delta>
<volume>Migration\Step\OrderGrids\Volume</volume>
</step>
</steps>
<source>
<database host="xxxxxx" name="database" user="user" password="password"/>
</source>
<destination>
<database host="xxxxxxx" name="database" user="user" password="password"/>
</destination>
<options>
<map_file>etc/opensource-to-opensource/1.9.0.1/map.xml.dist</map_file>
<eav_map_file>etc/opensource-to-opensource/map-eav.xml.dist</eav_map_file>
<eav_document_groups_file>etc/opensource-to-opensource/eav-document-groups.xml.dist</eav_document_groups_file>
<eav_attribute_groups_file>etc/opensource-to-opensource/eav-attribute-groups.xml.dist</eav_attribute_groups_file>
<log_map_file>etc/opensource-to-opensource/map-log.xml.dist</log_map_file>
<log_document_groups_file>etc/opensource-to-opensource/log-document-groups.xml.dist</log_document_groups_file>
<settings_map_file>etc/opensource-to-opensource/settings.xml.dist</settings_map_file>
<customer_map_file>etc/opensource-to-opensource/map-customer.xml.dist</customer_map_file>
<customer_document_groups_file>etc/opensource-to-opensource/customer-document-groups.xml.dist</customer_document_groups_file>
<customer_attribute_groups_file>etc/opensource-to-opensource/customer-attribute-groups.xml.dist</customer_attribute_groups_file>
<delta_document_groups_file>etc/opensource-to-opensource/deltalog.xml.dist</delta_document_groups_file>
<order_grids_document_groups_file>etc/opensource-to-opensource/order-grids-document-groups.xml.dist</order_grids_document_groups_file>
<map_document_groups>etc/opensource-to-opensource/map-document-groups.xml.dist</map_document_groups>
<class_map>etc/opensource-to-opensource/class-map.xml.dist</class_map>
<tier_price_map_file>etc/opensource-to-opensource/map-tier-price.xml.dist</tier_price_map_file>
<stores_map_file>etc/opensource-to-opensource/map-stores.xml.dist</stores_map_file>
<!--
In case bulk_size=0 it will be auto-detected for every document.
-->
<bulk_size>0</bulk_size>
<!--
Set direct_document_copy = 1 for better performance.
NOTE: 'source' and 'destination' databases MUST be placed on the same MySQL instance
and 'destination' user MUST be granted with 'SELECT' permissions on 'source' database
-->
<direct_document_copy>0</direct_document_copy>
<source_prefix />
<dest_prefix>pe</dest_prefix>
<auto_resolve_urlrewrite_duplicates>0</auto_resolve_urlrewrite_duplicates>
<log_file>migration.log</log_file>
<progress_bar_format>%percent%% [%bar%] Remaining Time: %remaining%</progress_bar_format>
<upgrade_customer_password_hash>1</upgrade_customer_password_hash>
<edition_migrate>opensource-to-opensource</edition_migrate>
<edition_number>1.9.0.1</edition_number>
<init_statements_source>SET NAMES utf8;</init_statements_source>
<init_statements_destination>SET NAMES utf8;</init_statements_destination>
<crypt_key>04a54072077cb6e32e54dee19b47cc3f</crypt_key>
</options>
</config>
You can try to join this, but i found it easier to do in two imports. If gallery tables give yu problems truncate them, don't worry, but remember to always have a copy of the original database, I got it wrong so many times, if you have any problem let me know I'll see if i can help!
Hope it helps :D