Mike, sounds as if you and I have similar experiences, albeit my cancer was most likely caused by HPV. But in terms of treatment I can readily identify with your distress.

All I can tell you is that it will get better eventually. The posts here are from some of our most knowledgeable family members (you're in the family too now, btw) and I hope you've learned much from them.

If you don't have it already you might ask for some viscous lidocaine. It's a thick fluid that you swish around in your mouth, maybe gargle a bit if you can, and it numbs the area. This helps in getting food and liquid down. You didn't say whether or not you were (still) eating by mouth. But it's a good item to have on hand even if you're not, for water drinking.

Hang in there! You're halfway, and you've worked hard and endured a lot to get here. You deserve to see it all the way to the end and out the other side. We're all here to help.