I would love to meet your son! He’s a rare one.
I agree with all the posters who recommended reverse engineering this. What work environment could he function in?
I suggest part of his continuing education at this point should trying this out on a low risk basis, part time jobs or internships in likely environments. Tech is a no brainer of course, and another path he might gravitate to might be academics. He’d probably make a great math professor, with his success in the tutoring Center probably the closest to work experience he has.
But he needs to train the flexibility muscle in his brain some more before he is ready to jump through real world job hoops, even in academia. I’m probably preaching to the choir here, and you’ve gone through a number of therapists, but you can’t give up on this.
It’s a pity that finances are constrained - he sounds like a perfect candidate for Oxford or Cambridge. No pesky gen Ed requirements, immerse yourself in math or sciences and follow your quirky interests on the side in the free time you have. And there will always be someone quirky enough to do join in with you.