Thank you for bringing your question to Just Answer!
Move very, very carefully!! His track record is not good at all. He may be grasping at straws after his ruined relationships. You say you're in "communication" but he's already saying he loves you? Keep him away from your child until you are quite sure he will be a stable influence. With his track record of having children and leaving, you need to do extra "due diligence" with this man. I would even suggest paying to run a full-scale background check on him. There are sites online that will do this for you.
It's been 20 years since you dated. You are clearly a different person, having gone to college and raising a child by yourself. It isn't as clear that he has matured and grown the way you have.
Your instincts are telling you to be careful while your heart hopes that there could be a fairytale ending. His record speaks for itself. There are at least 3 women and 2 other children he has left in the dust. Listen to your gut.
It would be worth a session or two with a counselor to hash this out in person, but my opinion is that this man has shown you who he is by ignoring your daughter for 20 years.