Bless your heart ~ I'm so sorry. I know this can be so difficult to live with.
You know, since the 19 year old lives with you, you CAN make him go to a psychiatrist! Either that, or out on the street! There ARE threats, you know. LOL I'm not saying that it will do any good, BUT perhaps once he gets there, it COULD start working! Stranger things have happened, ya know.

It might just work! Just make sure that either you or your husband DRIVE him there and pick him up -- and you may have to call and make sure that he really DID stay there and see the doctor! LOL Or you could wait in the waiting room for him while he sees the doctor.
My family is all messed up too, but most of us have the same thing -- depression. So that helps.

We're all a bunch of sad, pitiful beings. LOL
Are you making sure that you're taking care of YOU??? And I don't necessarily mean just MENTALLY either. You sound like you're exhausted mentally, spiritually, and physically!!! Can you get away for awhile? It would certainly do you some good !!! Perhaps you and your husband could take off for a few days, huh? Wouldn't the 19 yr old be ok by himself? You two need a break!
I wish you the very best!! Please take care of YOU! God bless and take care. Hugs, Lee