What should I do?

I’m so at a loss of how to handle the situation I am in. If anybody could give pointers that would be amazing. My son will be 4 in may and right before he turned a year and a half we met my now husband. But let me go back. My son’s biological dad has hardly ever been in the picture. He’s maybe seen my son 10 times before he was 1 1/2. He is supposed to pay child support but has only made a few payments. The bio dad has not spent a holiday or birthday with my son and his family is not involved either. Let me add he has a daughter a year younger than my son and has been steadily involved with her. My husband and I have been together 2 1/2 years and the only father my son knows is my husband. To him that is his daddy. I’ve had the bio dad message me asking to sign his rights over, and he bails out. He doesn’t ever text, call or anything. Well we had a court hearing and he just asked what he needs to do to see “his son”. I’m at a loss on what to do. My husband and I want to go through with adoption but with the bio dad being so stubborn he won’t sign his rights over. Anybody from an outside point of view please give me some advice. My son does not know his bio dad and hasn’t seen him since 2019. Do I let him see my son when he is a complete stranger or do i wait to see if he tries consistently to see him ? He’s never kept his word and goes from house to house depending on which girl he is seeing. He doesn’t own a vehicle or has anything for my son. Just last week we did not hear from him for over a year and he texts me asking what he needs to do.