You can start with FAFSA first. Then try his high school website. I know they offer scholarships. Fastweb.com is a good place for scholarships, Collegeboard.com too has much to offer, as well as the college websites themselves. Try to narrow it down to some colleges he may be interested in and start applying for the money. Now is the time to start doing that.
Grants can be found at the school websites - not sure if the other two sites I mentioned offer the grants. We, unfortunately did not qualify for grants. They look at the mom and stepdad's income together which is my case as well.
The student applies to the college, gets denied or accepted for grants, applies for the Stafford Loans that are offered and gets some money. The parents go through the process of applying for the loan,( I think you are also able to forego this process and just tell the school he is on his own) then you either get accepted or denied...either way you can tell the school that he is on his own, you are not taking a loan out. This will give him more Stafford Loan monies.
My son worked at Jewel part time and saved a lot of money toward school. Just to give you an idea, he goes to Western Illinois - where the tuition amount remains the same all 4 years. We did the above steps, and he ended up getting his room paid for the first year, and received about $10,000 in loan money. The remainder he was responsible for was about $125.00 per month for the year, plus books which were $700.00. We told our son he is responsible for the first two years of college, we will pay for the last two years. That way if he messes up, it is on his dollar, not ours.
Not sure about the accomodations for special diets (I am familiar with Celiac's Disease), but quite possible he could get money toward school if this is considered a type of disability.
Good luck with all your endeavors.
C. T.