Thinking out loud and looking for a path. (parenting)

I think I know where my wife and I went wrong with our son, who is now 18 and a lovely human, but it’s hard to fix. I think that I am a member of a group of parents who wanted their kids to grow up in a world without fear or stress. I have had a lifelong relationship with anxiety; I am now 49, it used to be called nervous stomach, but it is really so much more than that. I have had an extensive and helpful experience with the mental health system. I didn’t want that for my son and in my journey as a parent I may have fostered, in my son, the very thing I was trying to avoid. I am not parent blaming and shaming. I have a 16 year old daughter who handles anxiety in a healthy way. She may have seen her brother struggle and worked hard to push through when troubling situations arose.
My wife and I are artists, we work at home and the kids have always been around us. My son is a brilliant funny kid who was asked to leave preschool because he didn’t seem to be thriving there. He has always been a bit of a Holden Caulfield. More content to watch and judge but then wonder why he is not getting attention. Once it was time for him to start school he was excited. He returned home that day saying that he didn’t learn to read. As I put him in the car the next morning he asked where we were going. I said school and he said SCHOOL?! His relationship with school was troubled ever since. He would have friends at school but not close. He got known for being funny, but would walk down the hall making animal noises as a way of attempting to interact with people or get attention. On the subject of friends he does have one close lifelong girl (female) friend, she has been his audience and his nemesis. They would laugh for hours and my son would relay to her that he was learning the piano, or writing a mini novel and she would show up the next day playing the piano and with a novel started. This kind of competition would stop him in his tracks and he would never touch the piano (e.g.) again. When it was time to do more serious homework (grade 5 or so) he wouldn’t even know where to start the simplest math. His would get anxious/cry/cough/gag, etc. When presented with any task his thinking would go into some sort of panic. I would say he is almost unteachable. Even when I was working with him trying to explain something in woodworking he doesn’t really make eye contact and seems distracted. Incredibly he does seem to retain info that he is interested in. In grade 6 we pulled him from school and went with unschooling (don’t judge, I have a teaching degree and am prepared to defend unschooling) I am; however, willing to entertain the idea that removing him from the structure of school might have had its downsides. He did (does) have lots of friends from the unschooling community. If I could sum up his struggles (and possibly our mistakes) it’s that every change and contact in his life has been made by us (parents). If given his own choice he would say no to almost every outing/party/trip/hangout. He loves movies and movie criticism.
In his early teens he watched Rocky (we had begun to prod him towards exercise) He got the whole Rocky sweat suite with hood and all and went out for one run. Every door that he has seemed even slightly interested in looking through we have thrown open for him and made available any of the resources he needs to move forward with his interest...then he loses interest…then we push a little…then he retreats. We have shamed him for this behavior out of frustration but we now know that his struggles are deeper than a kick in the *** can fix. We did get him through his driver’s license, but it was all our doing. There was much anxiety, sleepless nights. He now has his license and will not drive, and if you drive with him you would agree that it’s a little scary. He is way too anxious to be a safe driver. He knows the rules of the road but you can tell in his eyes as he tries to go through the proper movements; shoulder check, signal… there is a whirl of information running around in his head that it not attached to events in the outside world.
He is now in college; at our prompting/paperwork. By all reports he is a good popular student, smart talented with friends, but when he is home on the weekend he can’t do anything else but worry about Monday. He says he has no friends, he doesn’t like anyone in his class, says he is the worst in his class and is now not interested in this area of study. Outwardly you would probably just think that he is a little shy and awkward, but nothing more. He has gone through about 4 psychologists, who all gave him breathing exercises and thought journals which he finds useless almost to the point of being offensive. I would venture that he is smarter and more introspective than most kids his age but with a distorted self-image. He has started an SSRI, a few months ago. He says in his down moments, especially to his mother, that he can’t see having a joyful life. That is heartbreaking and scary. Our friends and family seem to think he is fine and just putting on the sad face for us. That may be part of it but with my experience with my own mental health I think he is depressed, too depressed to help himself and has GAD but we first have to deal with the depression.
Thank you for letting me ramble. Does any of this seem familiar to any parents out there?

I don't think you caused this. It sounds like a much older version of my son which is on the autism spectrum. Best bet is for him to get a full psych eval.

I hope you have found some answers by now but it almost sounds like what I deal with- avoidant personality disorder, only a therapist/pdoc can diagnosis honestly but it may be something to look into.