Wendy,
My first thought is will he take it if his Doc gives him an antidepressant? I know I needed one and wouldn't accept it at first. My Doc asked "Why are you refusing my recommended meds and treatment?". I hadn't really thought of it that way. I was in the hospital and just WANTED TO GO HOME! I did start taking them then and it helped.
I know my case is not the "norm", as I was desperately ill for months after treatment and almost didn't make it, but it seems that depression at this point is not unusual. I should think that it could only help him to know that he's not expected to all of a sudden be all better now that treatment is done. The treatment is very hard on our systems and takes a while to heal and recover from. It will happen, though, just more slowly than any of us want. I don't know him so this is only a suggestion, but many men feel that they always need to be strong, tough, etc. Could he be feeling like he's a failure in that because treatment's done and he's not 100% fine now? Maybe some of our guys will weigh in here and offer their suggestions.
As far as the permanent and long-term effects - well, none of us really knows which or how bad or if. I'm still hoping for saliva to return at least in part. And I'm working on getting the surgery I need in order to get teeth. My real swallowing problems didn't start to get bad until a year after Tx, and the greatest part of that problem has been solved by throat dilation. I know that a huge step for me was to accept and embrace my new normal. I needed to go through a mourning process for the loss of the way things used to be but would never (or maybe never) be again. This happened for me over a year after treatment ended.
I don't know if anything I've written is a help, but I know this is so very hard on you, too. It's heartbreaking to see a loved one in so much pain and feel so helpless. It will get better, though, for both of you. That's a promise.
Lani