There is all the hope in the world that your son can gain the self confidence and esteem that will help him rise out of these problems. He is so young. Just recognizing these behaviors is already a step forward.

It is hard for me to offer advice, because I shared the same symptoms as your son at 8 years old and I am still overcoming my problems at 27. I have never been diagnosed with AvPD, although I have every symptom of it, so I browse this forum sometimes.

Building self esteem and seeing his own strengths would be of great help - and then to be able to contradict his always/nevers by reminding him of the times he was successful.

I have an idea that might sound strange at first, but: enroll him in a Karate dojo with a good reputation for working with children - and a good reputation in general. My little brother joined a small, privately owned Goju-Ryu dojo, and the Sensei was extremely supportive of children, there were even some mentally disabled kids there (my brother included). It is very important to find the right Sensei, me and my mom lucked out for my brother.

Each person is treated at their own pace, and the sensei(s) and older belts offer support and encouragement. Private classes would be available, so that your son would not feel competitive with other children around.

The spirit of Karate is self discipline, self love/respect, pride, enrichment, and personal growth. A good dojo can become like a second family - that is how it happened with me, my mom, and my little brother. We felt like a part of a big family. Much emotional support and understanding of personal difficulties. I always felt safe there, I could leave my apartment and go sit and watch.

I went on a little longer than I should have about karate, but I wanted to offer a possibility.

If not that idea, have you considered counseling? Or since you believe he is very intelligent for his age, actually asking him how he feels about seeing a counselor?