"For about three years now, he's been playing Daddy."
"(D)oes he owe anything morally to this child". Yes, I believe he does. He knowingly, and without deception, brought the child into his home and made certain promises to her. He should keep them. In addition, since he instituted a father/daughter relationship with the girl over a 3 year period, he is morally bound to at least try to maintain ties to the girl after he and the mother part ways. I most cases I have witnessed, the mother does not allow contact with her ex-boyfriends. Perhaps a review of the mother's moral obligations is in order.
Does he just get to use her and send her back to the Pound?
Since her legal guardian did not bother with the paperwork, legally he does. The exception would be the "promises" made to her, which could be interpretted as a legally binding verbal contract. As I stated earlier, I believe that he has a moral obligation to the girl, but he has no legal right (the mother can block him) or responsibility (other than specific promises) to the girl.
I see a clear line between legal rights and responsibilities, and moral ones.
Thank you. Actually, I see the two circumstances as interestingly related. The flip side, as you were. If a man deceived can get off the hook, it would seem the consenting surrogate father should not be able to enjoy a traditional benefit without some thought to responsibility.