@crabby55 I read and reread your post...it's indeed heartbreaking to see one's spouse sink into a state that only sounds getting more hopeless, specially when you try to be supportive. Indeed therein lies the glimmer of truth -- and hope.
Your husband Buried depression with overwork, and that shows the problem was never faced; he had depression all along.

As an 82 y.o. I never had depression except maybe a short few months or less when there were Real problems with survival. In your case, your husband does not seem to have any Real problems of life about survival. So what's going on.?
I have read -- and do -- a lot about mental health especially about addiction, anxiety and depression., issues that are common in the affluent world. Why?

It seems humans do not live for survival needs alone and that's why we often times live even live difficult lives to do what we Want From Our One LIFE. It is also called finding Our Purpose. We want to Matter in this world, not just a cog in the humanity. Thankfully each comes with desires and gifts that society can benefit from. It is thru such use of time that gives us a sense that We Matter, that We Did what was Important. It could be something as simple as helping those who were just struck with bad luck. Or children who have parents who are not able to help with their children's homework. You get the idea; we all can find what is a Useful/Gratifying work that one can look back before going to sleep and say: I did use my day in ways that Mattered to Do Good. Some call it finding Purpose in life.

I retired at 67 so that I could devote seven days a week into what I aspired to. I had a one-day anxiety attack that choked my breath. I came out of it by basically reminding myself in life great disappointments do happen. I sat with myself confronting myself, and that was how I never had it again. I declined professional help. I feel better for it as I Did It Myself.

Your husband too needs such little (or large) triumphs to remind him that his life matters not just to himself but Others. To make a Good society, a Good Nation.

I eat right and stay active not because these are good for health but because I Need Health FOR doing the good I am to do in My Life.
I hope you can help your hubby for a great life that awaits him.
Good Luck!