No answers for you, just some more things to think about...
1) I think you'd have to question the value of him completing the "three year cycle" at this point. If there's no value, then there's no guilt, right?
2) Homeschooling can be a GREAT option... but don't dismiss school based on anything you've read about VSL. There's not a lot of science behind any of that. For what it's worth, I'm a VSL, and if you measure such things in terms of honor societies and AP test results, I excelled in school. My VSL DD8 does very well, too.
We recently had a good conversation about the nature of VSL here:
http://giftedissues.davidsongifted....core_Pulls_the_Others_Up.html#Post1520793) Hard to say. If he's not reading yet, then K sounds like the right placement. There's a lot more to the day than math, so if that's the only area where he's advanced, it might not be a bad option.
Even in a school without a gifted program, there are still options. He might accelerate a year after K. He might be placed in a mixed-level class and do the math with the older group. He might leave the class and go to another one for math.