First of all, your teacher gave you a gift card? I would be flabbergasted if a teacher did that. Ok, just had to get that out of the way.
One thing you could ask about is reducing the written load if he demonstrates he knows the concepts. So let's say there are 20 math problems on a worksheet. Maybe he could just do the even ones? And only do the odd if he has problems with the evens?
Just a thought.
Asking for extended time on work is a good idea, or not being penalized if he turns something in late.
For your last paragraph you could say something like "I noticed that some of his grades on his current report card are quite a bit lower than last year, and I am concerned about why this is. Do you have any insights?"
