I am a married man with depression, and I can relate to his end. When I am in my bad spaces, I tend to be pretty hard on my wife. I can even see that I'm doing it, but it's hard not to. I have learned and accepted that I needed (and need) help. I am getting treatment now and while life is not all roses things are much better.
I agree with others in that if he doesn't want help and won't go see a doctor there isn't much you can do. He needs to want to get help. I do have one question if you are willing to answer. What does he believe he is dying from? I have anxiety issues also and have often been unrealistically convinced that I have some disease that I am dying from. Not sure if it's like that, but thought I'd ask.
Hope you are able to find some support on here!