Oh, OP this sounds very familiar. Have a 🫂. DD has autism (PDA profile), ADHD, anxiety, depression and was a school refuser. This caused conflict between me and DH, who likely has undiagnosed autism himself. He really couldn't cope with parenting DD so I was the default parent and struggled so much.
What really helped us was lowering the bar, taking the small wins, and simply being realistic about what DD could manage. I started off trying to get her up at 7.30 am, and would keep trying until about 1pm, at which point I gave up. We started seeing a psychologist who helped us understand that this was actually counterproductive. This helped in several massive ways. First, we had professional guidance as to how best to help DD. I could use this to explain to DH why a more relaxed approach actually worked better and strictness was just making things worse.
We were also able to work out (with the psychologist) what was keeping her off school and trying to sort that. Making the decision (with school support) that DC would concentrate on the important subjects and just ignore others completely took a lot of pressure off. For example, DC was missing entire days because of anxiety about 1 lesson, so school agreed she did not have to do that subject,(actually she dropped 3 subjects) which meant it was far more likely she went in. This meant an official part time timetable, where sometimes she was at home and sometimes had free periods in school.
Also, if some days she was just really down and said she was unlikely to make it in today, I'd just leave it and not worry. The reduced pressure really helped and meant everything became much more calm. DD started making an effort to go in on the days she had important subjects. The big thing was support from school, based on the recommendations from the psychologist. For DD, this was the part time timetable, no homework pressure (wasn't chased if she didn't do it), and outside of school doing things she found enjoyable and relaxing, but if she didn't want to go one week, that was fine too.
It just gradually got a lot better and we now live in a calm household where everyone gets on again. DD got good exam results in the subjects she did and now goes to college where her attendance can still be sporadic but she's doing well on a course she enjoys.
I'm sorry this was so long, but I wanted to share our story as you sound so much like we were years ago. I hope you can find a way forward that works for your family.