Update:
We went to a big event with a lot of our extended circle of close friends... uh... you know what I mean, right? The close friends who live far away, so we never talk to them, but when we do, it's like there was no gap. yeah, those ones.
Anyway, DS spent about 5 hrs in a mixed-age group with about 20 kids from those parents. Apart from getting lots of tokens for the stuff he put in the competition (:)), he fit in with the group just fine. He was certainly not typical in the group, he spent most of his time with the older kids, and he was somewhat "alone, with company." But he was comfortable, confident, listened to, even when he was doing something different from the other kids, he did it co-operatively with them, they gave him his space, and he gave them theirs. He'd, like, say "I don't want to pretend I'm in the fort" and they'd, like, say "ok, but can we pretend you are?" and off they'd go.
So, I'm not sure quite what the mechanism is, and I'm not minimizing the differences between him and the other kids that were there, but I think a big part of our problem is just finding the right group. Something is happening very fast that is putting him in a bad place. Probably the reactions to his first couple of comments.
That doesn't make it easier to find the right group of geographic locals, but at least it means we know that really is what we need to do. It looks like he's going to be starting a slightly geeky class in January. Cross your fingers for us!
Thanks, guys.