Ok, leaving aside for the moment the fact that you're being vile about children, I do understand that it's him you want and not his children.
I've said before on step-threads (and I speak as a step-daughter myself with a step-mother and a late step-father) I have nothing but admiration for women and men who do manage to love their partner's children. I just don't like children enough, generally speaking, some I like, some I don't, so for me personally, to discover a man had children already, would be the deal-breaker and have me heeling it off into the mountains.
You have to decide if you want this man at all costs, or not. If you want him, then you get his daughter. And you're going to have to try and make that work. You are the adult here, not her. It's part of her job description to be tantrummy and stroppy about her Dad having another woman. You are going to have to make the effort above and beyond.
I wouldn't take on board too much the thing about her telling her Dad not to have any more children. She'd probably have said that even if it was her own mother. That's just another typical stroppy 11 yr old thing to say, isn't it? (babies=sex=mum and dad having sex=gross)
He has children, you have a child. Do you want another child? Does he? Because whether she wants him to have one or not is not that relevant.