Has DH had any form of counselling to do with the mental side of knowing he has, what is in effect, a terminal illness?
For cancer, Macmillan are great at things like that, but I'm not sure whether such a thing is available for other conditions? If so, it may be really worthwhile to look into it.
Knowing that your "days may be numbered" can change a person, even if only for a short time, while they come to terms with it all a bit more.
It certainly changed DM's outlook on life, she was angry at the injustice of it all. She was slightly younger than most of her friends, and all around her she could see people celebrating their 70th, 75th or even 80th birthdays when she knew that she would probably never make any of those herself. There was a huge "why me?" about it all. Illness is very unfair, very cruel, it's natural to have more anger for the world I think.
For DM, it was Macmillan who helped her - through just having that completely impartial, independent, person to talk too. Someone who understood (as much as another person ever really can). They also got her to concentrate on making whatever time she had left as happy as possible, and not raking over every little thing that had ever happened in the past (which she was doing).
It may also help you to have some counselling. Not because you need to change anything, but because you might benefit from someone impartial to chat to? To get things off your chest a bit, as it were?
It's finding a way to make him realise that he is completely out of order being a cunt to you - whilst being sensitive to the fact that it's him this illness is actually happening to. You wouldn't want any huge rows or anything just now I imagine.
Your MIL sounds great by the way - 
for both of you!