Mrs W

Constipation could be a big factor in his discomfort. Pain meds will slow down his bowels and the slower they move, the more pressure feeding through a pump or push feeding will place in his stomach. Once the pressure becomes high enough, the body will relieve itself the only way it can, (vomit).

You might also try a regimented schedule of feeding, (time and volume), with enough time between to digest before adding more. Getting and keeping SOME calories is more important than forcing a pre-determined amount into him and losing most of it and his meds to vomiting.

I've been there and although it sounds ridiculous, once the bowel movements are synchronized with the feed intake, a lot of the nausea and vomiting issues may resolve themselves.

The Trismus will probably get worse during the treatment phase and the pain attached to the stretching is not something I would recommend adding to his daily regimen now. (However, as soon as he can tolerate the pain associated with stretching, he should. When he does, he will have to very aggressive about it.)

Good Luck