Your son can still be a P5 prospect, schools are just looking for more consistency at this point. Topping at 87 then 83 then 86 then 84 is a bigger issue than 85 every time he takes the mound. The velo differences probably tell coaches that he is either injured or doesn't have proper routine/training to maintain that peak performance yet. It sounds like the latter, and it sounds like they are still interested, just waiting for him to correct that part.
If he doesn't have it yet, get him in a routine. Scheduled bullpens and a throwing schedule. stretching, running, etc. Especially if he isn't throwing a ton in HS yet. Seems like you have some good guys in your corner, I'm sure they can help.
For now I would focus on getting back into form. Velo up, proper mechanics, good shape, etc. I wouldn't hit any of the big events until he is 100% back to normal. At the end of the day your son is a 6 ft lefty who can bring it in the upper 80s, who plays for one of the top organizations in the state. They will be playing big games, he will get plenty of looks, that's not the problem, it is looking sharp every time he takes the mound. Your son will be fine.
Just don't disclose the ACT scores to schools yet. He took it very early and simply put, they're not good. Have him take the ACT/SAT again in Oct/Nov of his junior year and see how he does. There are still plenty of top baseball schools that are test optional for college applications (MS State, Wake, etc).