Hello @dloliver. Radiation side effects are unfortunately part of the process. However knowledge has improved in this area. Certainly when the tonsil area is radiated this will affect several vital areas of the throat and mouth.
Proton beam therapy is far more accurate and less destructive than photon but also in many cases more expensive and may be refused by insurance. A few places will often offer proton at the same cost as photon, Mayo Clinic Rochester for one has done this. Not sure if that applies to all or just specific cases but one can certainly ask.
Paramount question while in search of a radio therapy clinic and oncologist is "what is the experience in this specific cancer?" My radiation oncologist with years of experience only treated two patients with Squamous Cell Carcinoma prior to retirement, me being his first one. I had issues.
On the bright side, HPV16+ has been treated successfully with surgery and drugs (not Chemo) only, no radio therapy. This is only in the past ten years or so, so we don't know if it is everlasting. It won't hurt to ask a cancer clinic or large hospital with cancer specialties if this is an option.
I realize your world is being turned upside down, this is a battle you never sought. Never the less, this is something you now have to deal with, something that happens in life while you have been making other plans. I and others are here for you. I can listen to you. I can make suggestions and help you through the rough patches to come. I cannot carry you but I certainly will not leave you as I know the fight you are in.
I myself am now twenty one years out with issues in between that in time have been dealt with. Have lived a full life, traveled, loved my family and friends, and enjoyed each day God has granted me.
"Courage". "Never Surrender". Words often spoken by a man whose statue in Parliament Square Garden in London, whom I have often looked upon for encouragement, Sir Winston Churchill. Perhaps you could make a goal to visit that place some day. You will get through this.
Sorry for the long-winded reply.