Hi Lorie,
My experience was almost identical to Karens. It was a couple of months post Tx before things started to slowly improve. I also did it without a feeding tube.

One thing you mentioned that caught my eye was antibiotics. With dry mouth they almost always cause a thrush bloom. A Nystatin swish & spit like Mark suggested or diflucan will knock it out. Thrush infections can be very serious if left untreated. They can become fatal if they go systemic.

Early post treatment is a very hard time. Make sure that his pain meds are adequate. I was on pretty heavy duty pain killers a good 2-3 months post Tx. It took a long time for the radiation burns and blisters to heal along the sides of my tongue which were the most painful. The good news is they did heal. The skin on my neck was the first to heal. The back of my throat - the last. I used to take 2-4 15mg morphine tablets prior to eating or drinking. I also used "pink magic".

The thick saliva and post nasal drip just stopped one day (it seems like a month or two passed).

About vitamins, in the book "Living Well With Cancer" by Katen Moore and Libby Schmais, they don't recommend anything other than a daily multivitamin. They recommend clearing it with your nutritionist for any other vitamin plan and never megadoses under any circumstances.

I can certainly relate to his frustration having been there myself in the not so distant past. I promise it WILL get better.