I am right there with your husband. All I can say is its difficult. He needs to connect with a higher power. Not sure what faith he has or has not but his is a connection that I think is important. He needs to know that everyday Dr's and researchers are working so hard to find a cure. Remind him that people are praying for him.
Try meditation, try spiritual books and DVD's. I am a research junkie and its my background but I find great hope and strength in reading and sharing data on cancer discoveries.
Its hard to feel good when in pain and despair.
Can you think of anything he can do to help someone else? Or a Hobby?
We are at our best when helping others.
Good luck but I know where he is and I know where you are because I have been a caregiver too.