Don’t sweat the will. Unless your parents are particularly wealthy, it’s not likely there will be that much to inherit once they both pass. Now you are completely free from their control… Mental health is a thing and many of us know that first hand. Counselors, psychologists, or a psychiatrist can help you dealing with depression. Staying as far away as possible from jerks who would emotionally abuse you will also help.

I don't get the ideology that everyone is just mentally well all the time.

We might be getting into the "What is true" dimension here but when everyone in a story is toxic apart from the person telling the story I get suspicious.

Cutting all ties with your toxic ex sounds like a no brainer. Cutting all ties with your daughter, adult or not is very much damaging to both you and her. We don't know the whole story, but most of the time if a child is toxic to the parents it's something that the parent did during their growing up stage. I don't believe that once a kid is a adult the parent does not bare responsibility anymore. Especially that for a lot of people 18-22 is still closer to young adult than full fledge adult. My suggestion include your daughter in your therapy, grow together and develop a good healthy relation. Might be hard, but you'll be forever happy for doing so

I suggest I group session with a therapist, including your parents. maybe then they'll get it.