Ok, let's imagine you are both the same age. If that was the situation and he kept calling you his daughter and his little girl, I'd say it was quite weird. I think any fantasy about children is weird, but calling the girl you're f*cking "daughter" is just plain creepy. And that's not even bringing in the whole age difference.
I guess if you DO consider the age difference, then in my opinion it explains the fantasy a bit. He obviously likes younger women, so pretending that you are a little girl kind of adds up.
But, as John Schofield said, it's whether YOU think it's weird that is important. Clearly other people do, and the fact that you posted this suggests that you do too, so I'd speak to him about it. Someone else said that if you're OK with it and he's respectful and treats you normally outside the bedroom then that's fine. But I get that you're not OK with it, so you really need to talk to him about it. If he respects you, he will definitely stop it if you're weirded out and its turning you off sex or even off him completely. If he refuses or complains or whatever then he's not mature and he doesn't respect you. Simples.
If you think it is getting weird, then it is getting weird. You need to tell him that you are not liking this and would prefer to stop it. if he respects you, he will be cool with that. If he isn't then you really know that things are getting out of control
Fantasies are just that. You could be a schoolgirl or something else. You could make him a CEO or whatever. There's nothing wrong with it as long as he's respectful to you outside of the bedroom. It is just something that turns him on.
It does sound like it's getting a little out of hand, especially given that he is so much older than you are. That ring of potential reality can definitely interfere with the "it's just a fantasy" mindset. If you feel uncomfortable with it, talk to him about it, and see what he has to say. Let him know that you want to make him happy, but you weren't expecting him to take his fantasy quite so far. Hopefully you can work things out and come to a compromise. If you can't, or if he isn't respecting your feelings about it, then maybe that's a sign that you two aren't as compatible as you could be.
Seems a little weird to me. And I think you agree or you wouldn't have asked. I don't have a problem with fantasies and I try not to judge other people's (as long as they're not sadistic) but this sounds like he's crossing a line past the fantasy part. He wants you to call him that all the time? That's a problem and he needs to snap back to reality.