As far as how they check whether you are responding to treatment is done in a variety of ways. Looking for markers in the blood, CT or MRI scans, sometimes PET scans, but the gold standard is palpation and visualization (sometimes with a nasolarygnoscope) usually with mirrors. They can't really detect tumors smaller than 2mm so treatment is usually a "shotgun" type of approach anyway.

I did it without a PEG but I am in a minority. It sounds like a PEG is a wise choice. The PEG has to put in by a gastroenterologist.

I didn't have surgery so I cannot comment on it. I do know that some plastic surgeries result in nerve damage that sometimes repair themselves.

They also have devices to help in getting the mouth to open wider, others will comment on that I am sure.