My daughters father pulled that with her, and I would get all upset and it pissed me off. Until the day came when I accepted that he will never be a "father" to her. When he would say he was coming to get her, I wouldnt tell her b/c he would never show up. Sounds like this dad gets a case of the guilts then ocmes around. To me your child is better off with him not being around at all, then popping in here and there and being a butthead. If he calls I would say I am sorry you cant see him, and if he wants to then he can take it to ocurt, chances are he wont and he will be gone.
My daughters father pays his child support inconsistently, but I would rahter he jsut be gone. My daughter has someone she calls dad, and that is what matters. Sounds like your son has that too, if he wants to call your boyfriend dad I would let him, but only if you know that you guys are going to be married and are stable, otherwise if he is gone again, your son will have another issue to deal with.
I told my daughter (older now) that she will always have a void in her life for that male attention she did not get from her biological father, and (i have it too) that you cant find it anywhere else such as food, gambling, a boyfriend etc... This is usually what happens as the child grows up without dealing with the bio dad not being therem they have a huge void they cant seem to fill. Sounds corny, but for me and my daughter we filled that void with the thought that god is our new daddy, I am not a bible banger or even go to church. But this helped her b/c when they go to sunday school etc.. They are taught that god is love. I dont know, it still bothers her from time to time, and me as well with my own dad, but it is a pain that stays with you forever, jsut gets easier and less apinful in time. To me the sooner he isnt around, the better. Unless he has some "change" where he is going to be stable and consistent.