you're very welcome @Watchamocauli it's not an easy thing to accept, that you're going to have to up-end everyone's life, but in my case it was definitely for the best and that has got more obvious as we have gone along.
But as @DrinkFeckArseBrick (another fab name) says, be 100% sure that this is what you want first, as it's not for the faint-hearted and there have been many times when I have asked myself whether I'm doing the right thing. Thankfully the answer has always been yes, because if I'd been uncertain I don't think I'd have gone through with it - leaving someone I still loved is the hardest thing I have ever done, but because of the abuse I knew there was no option. And when his mother was abusive because of me leaving her precious boy, that made me doubly sure!
As you say, settle yourself first, and sort out the practicalities so that the only uncertainty DD needs to deal with is what's going to happen between you, her and her dad, not where she's going to live or go to school; ideally keep both of those as they are, continuity in as many areas of life as possible is good.
And then when you do tell her, keep it all as calm and manageable as you can, with lots of reassurance (she'll be much less rattled if she's confident she can depend on you to take care of it all) and plenty of cuddles. Lots of those because somehow that physical reassurance of your love really helps in this situation.