Complicated kid! Those are awesome strengths.
This won't come through for you in time for the IEP meeting, but I'd suggest queueing up for private testing-- as complete as you can get. The math errors, the written instructions-- those seem to me to reach beyond "disorder of written expression" into executive function and language processing areas. Can you find a private neuropsych who can test across the whole range of strengths and deficits?
Armed with that information, you will do better with the school over the longer term-- and you'll know if there's something to address, and how to target your efforts. IMHO far better now than later.
I wouldn't trust a school psych or district diagnostician to make recommendations for a kid this complicated. YMMV.
DeeDee
