A.M.
we are going through the same kind of thing. We won't be able to do anything about having my husband adopt because the bio donor will not sign over just because he is a spiteful _____ (fill in the blank with the most nasty thing you can think.) and the "legal" system is a joke.
Ever since I left that [what ever you called him] my daughter kept asking me if her name was going to be my last name now. I kept having to tell her no. my daughter was 3 and my son was 6 months, that was 10 years ago. Years went by and the best answer I could ever give them was this "you are who you are in your heart". after I met my husband and got married almost 6 years ago both my kids have referred to themselves with my husband's last name, they call him dad and the bio they just call him by his last name.
At school they have signed all their homework and well, everything with the last name they want and they have explained to the teachers why and their teachers have been very understanding and they don't make them sign anything with their legal name.
If I have to make doctor appointments or anything like that and they hear me they get angry, not with me, but that they still have to be referred as the other name.
so we are still in this boat and it isn't likely to dock until the ex gets arrested or dies or my kids turn 18 and can file a restraining order against him and change their names without his say.
tell your son that even if you are not able to go ahead with adoption right away, he is who his heart tells him.