Good advice from the posters. I am not a therapist, and so this is only what I have observed and read about, but there is overt depression, which your h is experiencing, and while terribly painful, it is clear to him and to others. As 25 says, he needs help and may be able to see it.
Covert depression is probably more common in MLC. I suspect that many MLCers have been silently depressed for years, and it bursts out at MLC, but they still do not see it as depression. They externalise it a lot of teh time on to their partner. If your h can get help it would be very good, but you cannot fix him. There are some very good books on coping with depression, and he might find reading one of those helful, or not. You know him best.
There is a book that a couple of my [formerly depressed] friends have read and found helpful called 'Depression: Your way out of prison' by Dorothy Rowe, who is an Australian psychotherapist who has worked in the States and Europe as well.
Hard though ths is, your h does realise he has problems. So many MLCers think it is the rest of the world that has got it wrong.