Hi Deblows -
I can see that you are thinking hard about this one!
A) It's so rotten when you can't speak up for fear of making things worse!
B) Sounds like you have a good overall plan.
C) Excellent observation that venting may be all your son needs be able to go back and handle the situation elegantly.
D) OTOH - you never know the long term price or when it will come to a head.
So - My advice is:
1) Journal like crazy about your past history of being picked on or watching other people get picked on, so that you can keep your observations in "Present Time."
2) See if you can limit his exposure to the teacher from behind the curtains - perhaps by getting another subject for single subject acceleration - what comes before or after math with the bigger kids?
3) Read one of the "I can solve problems" books by Myrna B. Shure, such as Raising a Thinking Preteen: The "I Can Problem Solve" Program for 8- to 12- Year-Olds. I've never been sure how to use these books with our Gifted Ones, but it always helps me to read them.
4) another good book is : Stick Up for Yourself: Every Kid's Guide to Personal Power & Positive Self-Esteem (Revised & Updated Edition) by Gershen Kaufman
5) document, but if possible, do it when DS can't see you at it.
This is one of those frustrating problems that take a long time to monitor and change, when what you really want is to fix it right now. It MAY be appropriate to look at it from the learning perspective - when a classmate was picking on our son, we told him - now is a great time to learn to handle this difficult person, because he is handlable, and someday you will run into an even more difficult person, and be glad of the practice. I do feel that handling peers is a lot different than being asked to handle a teacher, though.
Hugs and best wishes,
Trinity