Birth mom, knows who adopted son is, scared to contact

Hi... The son I put up for adoption is now 18 years old. I had a letter prepared to send him, and I had someone that was going to give it to him, but... I heard he's autistic. I saw him on social media, and it doesn't seem like a severe case at all, but I am hesitant to initiate contact because I don't want to cause problems for his adoptive mom or dad. This was a closed adoption. I've not had any contact whatsoever with the child since he went away when he was a month old. On social media, there were things I read that kind of disturbed me, like, a comment that he says his mother made about his 'birth parents not being married" and how he feels like it's "his fault." THIS really bothers me. :mad: I don't want him to feel like this is his fault. It seems to me that he's asking questions and they're not being properly answered. I have seven other children now, and I want him to be a part of the family if he wants to be, but I have a feeling from what I read on social media that his mother is pretty controlling, even after he's hit the 18 mark. Not knowing the extent of his autism spectrum (or even if it's that, perhaps it's asperger's or something, since he seems pretty functional from the little I've been able to see) I'm very stand-offish about initiating contact, even though I just want to give him a big hug and say, "THIS WAS NOT YOUR FAULT!" The priest that helped with this case is deceased now :(. I could have gone through him to get him a letter and I know he would have been able to read it and everything, but I don't have that advocate for me anymore. I need some advice. Does anyone know what I should do? I know who he is already. I live several states away from him. I don't want to interfere if there's a problem, but how do I even find out if there is one? And if his mother has anything to do with it, she'll probably stonewall any attempt I make, and she's already not answering his questions. Should I get an intermediary from the adoption agency? And will they ensure that they will speak with HIM and not his mother? What should I do?