Hi Amy,
I'm not a medical person, but I did go through about five months of treatment for squamous cell cancer in my left tonsil. I had six weeks of chemo and external beam radiation, plus brachytherapy and several surgeries. I was 52, and like your husband, never smoked and very rarely ever had a drink.
It's good news that your husband's recent scans were clear. I did not experience any swelling in the cheek area after treatment, but I did have some minor swelling during radiation treatments. I would advise if you have any questions about your husband's condition you should call or visit your doctor, if only for your peace of mind. Could it be a dental condition? Your teeth are more susceptible to problems after radiation.
I will tell you that in the 18 months since I ended treatment, I've experienced muscle spasms in my cheeks, jaws and neck area. I'm told by my surgeon friend that this is due to the nerves knitting back together. I lost quite a bit of weight so my face is thinner, and the facial and neck muscles seem to me to be much tighter after radiation.
The other issues, such as lack of saliva, taste, hypothyroidism, etc., took about a year to sort out. I still chew gum and carry a sports bottle with me everywhere, but overall, life has been very good. You're through the worst of it, that's for sure.
All the best,
Greg