Well, you are smart to ask this question. And the answer is that you will only know the answer to your question with TIME. Any relationship is a risk - is he worth it? Sounds to me like he is if he became attached to a child and understands his importance to that child. He would become that way with you and perhaps your own child/future child. He says he won't go back with the mom so you have to believe him. And then see what happens. I would give it a shot. Keep us posted - and hopefully the others here might even have experience with a situation like this?
As Judy says, time is very important here.
He said he had considered adopting the kid