Hi Larisa,
Sounds as if you're doing everything you can for your son. He obviously has terrific parents. :-)
As for the worrying about living away from home while in college, although your son is only 6, I can remember having the same worries when I was only a little older than he is and being nearly as upset. I don't have ADHD. So this particular thing is probably not related to the ADHD. I think at some point in a child's life, he comes to the realization that one day things will change, but of course, he's not old enough to really understand it. It's scary.
Good luck to you all!
-- Michelle in NV