Stuck pt-archiver query during purge
A much better way to purge a table by date is by using DROP PARITION.  See http://mysql.rjweb.org/doc.php/partitionmaint  Unfortunately, it requires adding partitioning to the table and changing some indexes.  This will be a very long (one-time) task for 1.2TB.
Meanwhile...  If 10000 is tunable, lower the number to, say 1000.  I suspect that other activities on the table are conflicting with the archiving scan.  By decreasing that number, the will be less chance of conflict, at the expense of the archive taking longer.  (No, not 10 times as long.)
(&quot;Sending data&quot; is useless information.  Alas, that is probably the only clue you can get.)
(id &lt; '3873782070'):  Is id INT UNSIGNED?  If so, might it overflow soon?