Hi JB
It sounds like you found some outlet for your DS. We did the same thing last year in K. The schoold work took about 5 to 10 minutes, then we went on to the fun stuff. This year it's been a little harder because of the change in School. Not much homework, read 10 min, some spelling words (the challange words have taken some time) and some quick math. 50 subtraction problems to complete in 3 minutes. DS is trying to get that one done. The good thing is that we let him add to this what he wants, We have a trade off of time if he does more reading, or more math, he gets time on his DS. This seems to keep him engaged and wanting to learn more.
It sounds like you are on the right path. In Public school last year they let DS go to the 2nd grade class for math. It was one on one with the teacher. Perhaps you can get subject accomadations over time. It took us untill late November to get that. The public school did also agree to let us use the John Hopkins on line math instead of the math in the calss for this year. We changed schools instead, but it was nice of them to try and work with us. They also offer moving him up for reading. Its great that you are staying on top of it.