Your son sounds like he is a very talented player. I think there are many here who have been in your shoes, and wonder what is going on here. Based on what you shared, I'm questioning the outbound communication by your son to these programs that have seen him.....you didn't mention anything there. It appears he is attending many showcases and tournaments but not getting traction based on your post. How is he introducing himself to these coaches, attending the showcase/camps and then following up? Is his travel/high school coach involved in the process or reaching out on your son's behalf?
There is a big difference between marketing and sales. Your son is marketing his capabilities, but it appears he is not really selling himself to these coaches. Selling is the grunt work, on-going communications, and operations that needs to happen to close the deal. I didn't get the sense your son was constantly selling himself to these programs, nor any mention of a travel coach helping sell your son's skills. It is possible he is doing these things, but you didn't mention it so that was my first thought.
JMO. Good luck!