I’ve got a different take on this. I’m just starting college at 34 with ADHD, I have learned coping skills and what meds to take through life experiences…
I tried college when I was 18, and I needed more structure then the college could provide. Have you considered renting/selling your home, and moving to wherever his college is, so that you can better moniter the situation?
Or perhaps have him take less classes or more meds to help cope? But it might just be that he needs to wait as I did, though hopefully not as long before he can complete college.