I also live in a state with no gifted funding or legislation. If you teach gifted, can your son attend the programs where you teach? Or are you teaching much older students? I would talk to some of your colleagues and ask them to help you put together some enrichment program for him to follow at home. I know how depressing it can be knowing your child *has* to attend a school where they are not learning anything new. I try to teach as much new stuff to my DD as I can at home. Thankfully she enjoys the social aspect of school, so attending for her is more of a fun social activity and there are some areas of the curriculum that she is still learning from, too.
As far as helping him be happy in his own skin, I would probably just let him know that he is a great thinker and that most people (even adults) can't think as well as he does. I would encourage him to have more patience and forgiveness with others (ha ha ha) and let him know that you fully understand what he is going through and encourage him to shine and do his best, regardless of what people think.
I don't know if you can ever take away that "odd man out" feeling but you can reassure him that he is exactly who he was meant to be.
