Types of radiation therapy and chemo therapy combinations

Hello - my brother was just diagnosed with HPV cancer and had removal of lymphs nodes through right neck dissection and removal of right tonsil. He is 56 and otherwise healthy and very active. There was cancer in only 1 or 30 lymph nodes but it was large and the cancer was outside the lymph node (extra nodal extension). They did not find cancer in the tonsil and he is now scheduled to go back for the TORS surgery to remove the lingual tonsil. They are unsure if they will find cancer in the other tonsil and think there is chance they will not find the primary site. He is told he will need radiation for 6-7 weeks and likely chemotherapy as well.
My questions;
I've been reading about Proton therapy radiation and it seems like it is better tolerated with less side effects. He is at Dana Farber and they seem to have an excellent Head and Neck program but I don't see on their website they offer Proton therapy. What can people tell me about proton therapy vs. traditional radiation and is worth seeking out a 2nd opinion at a center with proton therapy? I've also read about DART and wondering if others have chosen that?

Chemotherapy was discussed but there was no mention of immunotherapy. Wondering if others have been offered immunotherapy? The doctor seemed to indicate that although
he was leaning towards recommending chemo that it would be reasonable for my brother to decide not to choose chemotherapy as the research is limited. My brother has hearing loss in one ear already and I've read that one of the side effects of the chemo used for HPV is hearing loss so this is of course a concern.

Thank you ahead of time for any thoughts, suggestions or recommendations to further research and discuss with his team. My best to you all!