Thank you for posting, I am going to come at this from a different direction, I suffer from severe depression, and I can see the effect it has on my wife. from my point of view, a lot of help from those close to us can be "misguided", when you are depressed, hearing just think good thoughts or focus on the positive just simply does not work. You feel so low, worthless and helpless, you just don't see why people should care about you.
I found it helped me so much when my partner accepted I just needed to be alone sometimes, I would go for a walk, have a coffee and read a book. I am never pressured into saying what i am doing or where I am going or when I will be back.
its hard, but you need to let him fight his demons, you can't do it for him, however much you wish you could. Little acts of kindness that are not designed to try to get him to open up or talk are always welcome, a favorite chocolate bar, just given casually, "bought this for you at lunchtime" type thing, buying him a book if he reads, just random acts to show him you are there when he may need you will go a long way.
it is hard on you, human nature is always to try to talk things over, but some of what he may say could be the depression talking, try not to take anything negative to heart. I can see it is horrible for you, keep talking on here, check out friends and family threads and be there for him, he will open up when he wants to or when he is ready.
I hid mine, crashed badly and eventually went to Docs, medication helps. Also, local groups, especially male only support groups have been good for me. Not for everybody, but maybe see if any are about?