What I would try to do in your shoes:

I'd make sure that I'd pulled the plug with my ex myself first. I'd make sure that I'm not sorta interacting with my ex through my daughter.

I'd support my daughter in having healthy boundaries. She can say No to her dad anytime she wants. Can she get some therapy, even a few sessions?

You and your daughter can work up some plans to help her with the boundaries that she chooses. Maybe she wants to visit with her dad but she wants help setting a limit for each visit, she doesn't want him to try to turn her into the adult taking care of him, she doesn't want to be his caregiver. So, she can have other plans, other activities to focus on. She can practice being assertive.