Confused - I didn't post at first, because I have no experience of this, or the continuing confusion and disruption it causes, but I think that although you were very careful in the way you described your father's inappropriate behaviour, people feel very protective of the fact that it had such a profound and long-lasting effec on you and your sister. So, even an inappropriate lapse could effect your own little dd in the same way. And as many, many survivors have said, men do find a way, and it doesn't even take being alone. A game, the way children naturally affectionately sidle up to you when you are sitting on a chair and lean on you, a trip to the park and holding steady on the see-saw...
Of course your dd is a priority, and because of that, you feel that you will protect her with your life against anything. But should you have to feel like that?
I do believe, very strongly, in forgiveness and not causing separations where none need be, but I thin if I was your DH, I would be resolved beyond negotiation in my determination that my dd should not be with your father.
Is it possible for you to invite your Mum to stay with you?
Do you have a feeing that you want your dad to see and be proud of your dd, and as a consequence that he be ashamed of what he did, and that it will all be ok?