Wish I had some better advice. I AM your husband, except for the fact that, without a spouse, walking away from the job that drives me to the point of desperation and has at times driven me to the brink of ending it is simply not possible because there is no spouse for me to depend on. I get my butt out of bed and out the door to work, and I do my job, no matter how much I hate it because, even with ADD, I get that I would hate being homeless with a cat and a tortoise even more.
The one thing that helps me is that I have another “job” that I don’t get paid for, but which I love, I’m good at, and that makes a difference. It’s not always fun. It’s hard and heartbreaking, and a lot of nights it leaves me physically, mentally, and emotionally exhausted. It means getting off work at six, and immediately hitting the road for my other job, getting home between midnight and 2 AM and then starting all over again at 7AM. But… it gives me a life of sorts, and a feeling of competence and self-worth when I’m out there. All of the things my “real” job takes away from me. It lets me see the job I hate as something akin to chronic pain — something I have no choice but to live with, but which I refuse to allow to stop me living. Maybe your husband could find something like that — something he can put in the forefront of his life that gives him what his other job takes away from him.