There are some good therapies for depression and things can be better. One of my friend's husband has had major depression (the inherited kind) all his life. He is now on new medicine and he is thoroughly enjoying his life and is fun to be around. I wish that I knew the name of the med but perhaps a different psychiatrist would be able to help your husband.
Yes, kids are great and give so much purpose to life. I think that many of us would have more if things worked out.