Vash,
There are a few things that may be of help and as you mentioned, the lack of exercise is probably one of them. Sleeping while in a flat position may be another. The lack of fluids may be one part of his problems and the swelling yet one more part of the puzzle.
Hopefully, this post won't be too long, but I'll give it a try.
1- He needs to get out of the chair and push himself to walk a little bit each day. The reason I say this is that fluids do build up around our necks from the treatments in the lymphnodes which in turn causes the swelling. One way to help lower the swelling is to walk and gravity takes over and the fluids drain down towards our feet. A gentle massage around the face and neck help promote the flow of the lymph system as well.
2- I was told by my Radiation Oncologist that we may have to deal with fatigue issues for up to a year. Nutrition can help with that. Gotta eat and exercise, even if it is only 10 minutes a day to start.
3- Sleep in a incline will help the fluids stay away from the neck area, which in turn causes less swelling. The swelling also causes issues with swallowing as the swelling isn't just on the outside, but may shrink our passage way in turn causing breathing stress.
4- I was told we need to take in roughly 64 ozs of fluid a day. If he drinks a bit more water daily, it may thin out the mucus a bit. I still deal with some nasal drip which causes me to have mucus issues, but not as bad as it was before.I may soon return to the Salt and Baking Soda solution that I used during treatment to see if that has any effect on the mucus. I seem to remember that it did help me.
My Best to You Both and Everyone Here