What area do you guys live in?
If your son was on a top ECNL team previously, it seems he would be a lock to make the JV team in HS without issue at all, especially if he will be a sophomore?
Regardless, sounds like he could use a break and or get on a program with a good friend to re-kindle that passion.
I'd second the opinion to get him on lower travel team and let him shine on that team, specially if you're locked out of the top teams.
A good private coach can motivate a player and work on certain skill sets... like agility and technical play. Honestly, they should also be able to give you a sense of his work ethic too. If the work ethic is lacking, that would indicate his motivation is low and it is time for a break from more serious soccer. But they can't analyze his game play if he's not on a team. You might run into a dead end or get a hard truth.
You could also try sports psychology and counseling...on its about $100 per session. They can give you a good assessment after the initial session. But be prepared for the hard sell of attending 6-10 sessions to help fix the mental problems. That might be more beneficial than the private training.
https://www.kidssportspsychology.com
Also, keep waiting, don't panic, something might shake out this summer!
Good luck!