Have they ruled out thyroid? Usually the sore in the mouth is one of the first signs, along with vomiting. Since he is 11, it might be a good idea to rule that out.

I've got 2 senior cats here and worry all the time. Mollie Rose is showing signs of kidney probs. She drinks alot of water and pees alot. I know it's only a matter of time. I've been assured by the vet that she is comfortable (with the held of chlortimeton for allergies) and not in any pain.

Good luck with Morgan and please, keep us posted on Morgan.