They've prescribed <more> meds to help him stay relaxed, but I'm thinking that if we learned some techniques it might help too.
Some basic biofeedback might do wonders, I bought a unit from Radio Shack for $15 ten-twenty years ago that works on this same idea:
http://www.amazon.com/Basic-GSR2-Biofeedback-Relaxation-System/dp/B000E22DFE
And body scan can help as well:
http://www.amazon.com/Relaxation-Body-Guided-Imagery-Well-Being/dp/B0000AGUCJ
I used two items similar to these to overcome severe migraines many years ago.
Best wishes.