Not really convinced all the improvements that you made would make much of a difference. Not that they were bad things to do, but is seems that the real problem was 24 amps on a 20 amp circuit.
Maybe not as 'flashy' as getting all those new pieces, but I would want to split that receptacle off from everything else, and run a new circuit all the way to the panel. Yea, I know, that means a lot of crawlng in unpleasant places, and PITA fishing.
No room in the panel? Well, there are solutions for that, too. Of course, they invole lots more work....
