Hello. Thanks for the questions. It's a good thing you're doing for this guy.
I would just be as aggressive as possible to cure these issues. The stomatitis is essentially cured with full mouth extractions. I would remove the remaining teeth if there are 2 left and inflammation still present.
If there are still polyps in the ears and debris in the ears, then I would do a TECABO on both sides. This is where the ear canal is removed and the bulla cleaned out. This removes any inflamed tissue. It's the only cure for these recurrent polyps and ear infections.
If the attitude is all due to pain, you may find that the surgeries make him much more handleable at the vet from now on. No promises, but it's possible.
Here is a nice handout on the TECABO surgery for more info:
And one on stomatitis:
I hope this helps, let me know if you have any other questions.