My mom has bad bulging discs in her back and even though it is not the same thing as your husband, I found a gel pad at the local chiropractor's office that has worked wonders. She can sit on that thing for hours and not have any pressure on that area which causes excruiating pain. Yesterday, for whatever reason, she did not and she was miserable by the night.
As for comfortable places, has he tried just laying on the sofa instead of sitting? It's so hard seeing our loved ones with so much discomfort. I hope you will have some luck in finding some answers.
From one Cris to another...God bless ~
Cris
daughter of mom dx GBM IV 6/09