I second legal advice, and maybe speak with a child psychologist about how to approach the separation with your daughter. He could go with you to discuss his plan and the psych could talk about the possible impact this would have. To be honest, I see it as more disruptive to her than a clean break with boundaries around how things work. Unfortunately things like this usually get messy before they get better BUT it can work, if both if you seek advice together about how to make it as smooth as possible.

I'm so sorry you are in this situation. It must feel dreadful xox