Sorry for your troubles with your throat. Dryness for me so far has been limited to my mouth. Typically comes ad goes intermittently during day.
When really dry I use ACT dry mouth moisturizing gum and I believe it’s the xylitol things that stick between your gums and teeth. That’s been enough to date. My best to you

So far, my husband’s favorite is Biotene Dry Mouth Oral Rinse. He uses it sporadically during the day but always after brushing his teeth before going to bed.
He, too, had base of tongue hpv-16 sec with a lymph node involvement, stage 1(luckily caught early). It was caught near the end of evaluation for heart and kidney transplant due to a major heart attack. He had 35x of radiation but had 7 rounds of monoclonal antibody therapy, once per week, instead of chemo. This was in the summer of 2022 and he has been clear since then. It did stop the transplant evaluation but he’s doing fairly well, golfing at least once per week and boating. His most annoying side effect has been lack of taste, or rather food having a lack of taste and leaving a bad taste in his mouth.