I would suggest to stop trying to work through this via the forum.  Instead, use the option in Quickbooks under Help > Quickbooks Help > Contact Us to speak directly with a representative.  You'll want to find out right away if they understand the issue of how to purge a large number of old transactions from your Quickbooks 'Downloaded Transactions' panel.  And if they don't, then insist on speaking with someone who does know it.  When I finally was able to solve this, I happened to get lucky speaking to a rep who was familiar with the issue.  Multiple calls and service requests with other reps repeatedly fell short before that.  And even with the rep who knew the issue, it probably took 20 to 30 minutes to get through it.  So trying to find success in this forum's back and forth is not possible in my opinion.  Good luck!  (Oh also make sure they show you how to routinely purge future downloaded transactions as you go.)