I will share with you now op that I am the adult version of your dd (only difference being that I was abused by my own father, not SF)
I am still in therapy now, I hold my mother fully accountable for allowing that abuse to continue.
I have no contact at all with my father, and I barely ever see my mother. I don't really want a relationship with either of them, they are both utterly toxic in different ways.
My mother was too weak to leave, so she just turned a blind eye to the years of abuse. It was horrendous.
Do you want your dd to leave your life at the first chance she gets?
She may decide that you had your chance to protect her, and you choose not to.
You could have stepped in and stopped her being hurt, but you choose not to. You are doing untold damage to her keeping her there every day with that man, but you carry on.
Whether you like it or not, the buck stops with you.
The responsibility is yours to ensure as a bare minimum that she is safe and secure at home. You know she is neither safe nor secure. He is going to carry on tearing strips off her, you know this.
He is damaged and beyond help, why you felt someone so damaged was the right man for you and your dc, I have no idea, but you are where you are.
What you do now really has very longreaching consequences.
I would have loved my mother to take me away, I used to dream of leaving that awful life. No matter what the hardship I would much rather have grown up in a place of safety and love, to be able to relax, to unwind - to feel safe. The stress on a small child's body as they prepare for the next verbal attack, the damage to her is immense.
My heart breaks for your lovely girl, it really does.