You're going through the worst bits now, and all you can see ahead of you is dark. But it's a tunnel, I promise - there's a light at the end.
You have friends, and you have a family - I'm sure if anything happened, your sister and her husband would be there for you. But your mother isn't going to die any time soon!
You said you had migraines, and that's why you are unable to work full time. I don't know if you've been properly seen by doctors, but migraines most often have a significant stress component. My mother used to have horrendous migraines for years, and they were related to large extent to her own personal problems (she also had a toxic MIL, although my father stood up for my mother against her). Things got better, and her migraines are much much better now.
I strongly suspect that once you are out of the woods you will find that your migraines get better, or at least are more under control. You'll also make more, and much better, relationships, including (if you want) a relationship with a man who actually loves you.
As for work - as I said, let's see how your migraines go once you get your divorce and move on. But I have no doubt that you can take care of yourself. You can find more students, perhaps you can freelance - there are many options, but this is not the time to think about that. Now's the time to think about your half of the assets and make a clean break. There'll be plenty of time to think about your career then.
I think you are beginning to realise the extent of the suffering you have been through. It's a bit like a boiling frog - you don't realise how hot the water you've been in was until you're out. And it's frightening - change is frightening.
This is all completely normal, Elf. And yes, it's completely crap. But you should be very proud of yourself. It's not easy AT ALL, and you're doing so well. ((((((((HUGS)))))))) 