In my own case and I believe in many others, my future (and likely your husband's) is a matter of personal adaptation, work-arounds, and mostly acceptance. My xerostomia has not improved since the first 6 months after radiation. My water bottle is now as much a part of who I am as anything else in my life. It is like my wedding band, wristwatch, etc, always there with me. I hardly notice it anymore though it is always in my hand. I put water in dishes at retraunts with it, (to make pasta sauces wetter, to make mashed potatoes wetter, etc.) I I have learned to ignore the looks from those who do not know what is going on... even the looks I get carrying a water bottle while dressed in a tux at a formal event, which to many seems out of place, it just is what it is, and who I am. I do not think you are going to find your solutions in doctors, naturalists etc. it is in adaptation and acceptance of and to the new situation.
As to the cramps I can only state that mine have gotten worse as the years have gone by, and while they are aggrivating, the radiation damage has done its work and they are not going away. While an occasional massage feels great, what has helped the most is upper body exercise to take the load off of my neck, and strengthen supporting muscle groups, as the muscle spams seem to be worse when my neck is fatigued. I also have 3 herniated discs in my neck from a crash that also broke my collar bone, which exascerbate all this, and between NASID's and tolerance I try to find middle ground. Given what others have been through, and knowledge of how much worse it could have been, I have learned acceptance. To someone like myself who feels that I must always do better, be better, etc. this was a difficult journey. But at some point you have to realize that this is the best it is going to get, and live within the new parameters that exist. Life will never be the same, but it is sweet just to be here.