"Maybe what I need is for Dr. F to teach me math so I can understand it and can teach it to DS6!" (I still can't do the box quote thing.)

I have a friend who's father-in-law is a rocket scientist - literally - who worked on the top secret rocket programs in the 60's and 70's. A true mathemetician and physicist. Anyway, when my friend's kids have questions about math, they get sent to Grandad. Also, grandad takes the time to teach the kids in everyday situations about physics and math. Not in a structured way but in a "oh, look, there's a leaf falling from the tree, how fast do you think it is falling?" kind of way.

Maybe what you need is someone like that, maybe retired or maybe a whiz grad student, who will mentor your son after you have taught him the basics. You could pay him/her or maybe barter. I've thought about proposing this to my friend's FIL. You could keep a log of ideas he wants to explore and then have the mentor start with those ideas and see where they go from that. So YOU don't have to learn calculus in depth, just the concepts and then someone else works with him in depth.

And, I understand not wanting to crush his desire to learn math. I also think it addresses the "how do you go deeper at age 7" syndrome with which I struggle.

Don't know if this makes any sense but thought I'd toss it out there. I think you might be on to something that works for you but it might need to be tweaked to take less of the pressure off of you.

I'm off to tour a private school - still trying to decide what to do with J for next year. This one is a Montessori so I don't have wild hopes, but we'll see. (oops, didn't mean to get off subject.)