I am dealing with a similar situation, and I have tried several things, but some things I wish I had tried sooner because now I am worried that it's too late.
I assume you are workiing with MB stuff, that's a good start, after you know his needs very clearly from the questionnaires.
He definitely needs to get counseling. For him to have an objective party to clarify his thoughts and give him feedback, will help him. Don't try to provide that for him. You are not objective, and he won't view you as objective. Don't get caught where he'll take your advice as thinking you want to manipulate him.
Also! Have him talk to a doctor about depression. It sounds like he has some of the symptoms (hopelessness - things can never get better, helplessness - it's beyond his control to make things better). While someone is struggling with depression they don't have the additional resources to work on marital issues. Deal with this first!!! Focusing on the marriage first can worsen the depression and make it impossible to work on the marriage.
If there is any man who can come alongside and be a sounding board, ask. It's hard to find someone. If there's anyone you know who has been through depression before and understands the power of it and how to recover it can be invaluable. Read up on depression yourself: a good website with some other helpful info similar to this one:
www.midlife.com; do a search on the web - get informed.
Find counseling for yourself. You also need an objective viewpoint, and someone that can help you change some behaviors. Especially if you tend to take more than your share of the responsibility for the problems. You need to grow in new ways, but don't do so much of the work that he doesn't get stretched. *This is a hard one, though* How not to do too much, but then not doubt that you failed to try enough. Hopefully a counselor can provide realistic feedback.
Can you get community support? Church, family, friends? No one wants to stick their nose in your business, and it's hard to air your problems, but if you two have others to vent to, share joys with, to help support the two of you things seem more manageable.