Re: where to start...
You've received great advice here.
RUN, don't walk, away from doctors who wish to pollute your sons body more. "Balancing" and "meds" are 2 words that don't go together for a 5 year old.
Any food which your kid craves like that -
Sugar and refined carbs - are bound to be in the 'very bad for him' list. You do have the power to set the rules here and make sure he followes them, and if you ever get depressed when trying to do it, send another note out on curzezone and you will get support. Once your family realizes that *YOUR WORD IS IT* they will fall in line. The beginning is apt to be the hardest time, but only until they catch on.
Have you seen the autism forum here on curezone? You'll find a wealth of info on metal detoxification, and diet changes to rid your son of autism. There is one story about Miles that describes how a mother changed his diet and cured autism.
I got a very strong feeling when reading your note that an osteopath might be good to check out. not a chiropractor, unless its a really unusual one... (and they do exist out there).
LisaG