Ok, here's what I would do:

A) Set aside the Air Asia tickets. Pretend they don't exist.
B) Call United without mentioning the current itinerary, and try to problem solve the itinerary you're really after (BKK is just an intermediate stop AFAICT)
C) Be creative with b). Look at all your options - use the tools available here (KVS, Expertflyer, ANA tool) to try and get as close as possible to what you're looking for
D) Once you've found the best "new" option, see if you can adjust it to make use of the credits you have on AirAsia.

The process mistake I think you're making is that you're trying to do this by forcing a rescue of those flights you've already purchased. That may *or may not* be possible - and I wouldn't hinge the whole trip's success on that. Just pretend you never bought those tickets and reoptimize your current itinerary.

And, I strongly suggest you not share the booking stress with your (clearly stricken) wife. Sounds like she's not helping your calm-assertive energy.

-G