From what I see, your son is quite a pleasant, kind and gentle soul. I also see he is intelligent, however, very stubborn and once he makes up his mind on something, it will be difficult to change his mind. From what I can see, he is the kind of person that will try and deal with his abandonment issues internally and won’t want you constantly prying and asking him how he feels. He especially wouldn’t want you suggesting for him to go to therapy. For now, my best advice to you would be to make you son aware that you are always there to talk if he wants to and that you support whatever decision he makes about this other parent. Don’t push him into anything. Just create a safe environment for him that will help him to open up to you about his problems a bit more. Perhaps cook him his favourite meals, spend more time with him (don’t smother him), engage in light conversation with him about topics he enjoys talking about. From what I see, he doesn’t think about his abandonment issues often, it only hits him at random times or at night time when he’s alone and has time to think about things.