I believe that tests have "ranges" for a reason. I don't think that I would worry to much about the precise number; rather, they are merely two snapshots on two different days. All of your testing and information suggest that your DS is both quite gifted and high achieving.
One thing that can be done if the right IQ and achievement tests are done around the same time is a discrepancy analysis. DS's tester did this when he took the WISC/WIAT, and it was very interesting.
I think all kids, including gifted and HG+ kids, are different. DS6 is a DYS, but he DOES run around and play chase with boys his own age. He also plays with friends who are 9 and 10-years-old sometimes, and manages to fit in. He's a bit of a social chameleon. Then again, DD is pickier about her friends and less willing to be a chameleon - she also often doesn't care to change herself to fit in with anyone...she is stubbornly herself.
Best of luck with your advocacy - your son is very lucky that you are trying to help meet his needs!
