He sounds great, and just like mine. Memorizing math facts is not his thing at all. So boring, so repetitious... he hates it. The best thing I've found so far is to play games. Go Fish with math facts, math War, design your own board game, have him design his own game (and it might be something totally crazy that you don't even understand, but just go with it!).
You could also have a building challenge where he gets building materials for answering each question. 5+5, gets one LEGO brick, building block, k'nex piece, etc. You can be answering math questions too, and building your own structure. When you're done, have a battle if he likes doing that.
You could also get some foam blocks and write numbers on them. He could pick two (or three, or more) from a bucket. If he gets the answer right, he gets to use them in his castle. If he gets them wrong, YOU get to add the blocks to YOUR castle! He'll probably try pretty hard to beat you. It works in reverse too, so if you make a mistake, HE gets YOUR blocks. At the end, you could have an epic battle and try and knock down each other's castles. (You should probably lose on purpose :)
Can you tell I've been hanging out with a 9 year old?
Also, I find that the way I "frame" the lesson really makes a difference. Saying, "Okay, time for some math!" is going to go down worse than, "I have a great idea! Let's have an epic battle! We're going to build castles and knock them down!"
Your reading progress is amazing. I hope for the same thing for mine!!