Good on you for being ready to take that next step.
I think you need to be prepared for when you go no-contact with your dad, that keeping in contact with your mom may be impossible. It seems pretty clear she’s pretty under his control as well. Whatever contact you have with her, assume anything you say will get back to him.
Good luck in getting and maintaining distance. I know these things are difficult, but your father has shown himself to be a toxic hurricane. There is no benefit he can provide to your life.