I'm sorry to hear that your son has had such a hard time. Your description of him made me think of my own teenage years and how rough they were. I tried going to therapists and I took medication, but none of that helped. Eventually, I discovered that I wasn't really getting at the root of my problem, which was my social anxiety. I started a CBT program offered by the Social Anxiety Institute which really gave me a new perspective on life. I realized how distorted my thinking was and worked to change it. Over time, I saw a great amount of progress.
If anyone is interested, check out their website: https://socialanxietyinstitute.org/