I must confess, I was very anti-homeschooling before coming to this board. I would argue the typical reasons why it wasn't a good idea, but thanks to reading about other people and their children on this board I no longer feel this way. Background on myself: I have a Masters in Education and it certainly did not prepare me for my daughters giftedness and as I mentioned in an earlier post, she is only 3.5! We are not even in regular school age yet. My own education at one of the best educational schools in the area did not prepare me for the gifted child. Our educational world does not do the gifted child justice. They lump them all in a category and never consider the LOG and how a moderately gifted child is apples to oranges to a highly gifted to child; and apples to cars for a profoundly gifted child. I have no doubt that your son is on the high end of the HG+ range. (Highly gifted plus) Not that we have that much information about your son's school experience but I doubt that he is being challenged and the one hope you had of acceleration is (at this moment) not an option but I have to wonder if that would even be enough. I, personally, would not dismiss homeschooling. I suspect you aren't giving yourself much credit. Clearly you have resources in your family to pull from and you could always think outside the box. If you have a local university there ... think of the great opportunity he would have with students there: You could always hire a tutor from the university. And just because your father lives at a distance doesn't mean it isn't doable. Technology is there for video conferencing, among other things.
Don't think I am saying pull your child and homeschool, but if the reason you won't is those you argued then I just wanted to point out that you have options and the big one is your son will no doubt guide his education.
Also, are there any gifted schools in your area? Or college prep and charter schools? You might want to do a little research on methodology of the different schools in your area. IE. I was looking at a college prep school we have in our area and really like that they are progressive. Progressive is student centered and more project driven and certainly does not teach to the standards. Though their students do take a few of the typical tests it is more project oriented. It is definitely something we will consider for my daughter as an option when she moves into 6th grade.