This will not solve the bigger math problem, but I wanted to share the name of a book that my son and I enjoyed together which we used to supplement the more cook-book math. We loved working with the big concepts and where the math ideas came from. And the chapter on infinity saved me from those endless questions like "can one infinity be bigger than another?" that were driving me nuts. It's called "The Heart of Mathematics: An invitation to effective thinking" It's college level, but it worked well for DS at 10/11.
Apologies if I've posted this before; I just liked it so much I want everyone with a mathy kid to know about it.
