That happens. <reassuring pat on the back>

So it seems to me the big question is what don't you know that you need to know?
I think you probably need to get your child assessed. Until you have some idea what you're dealing with, you can't know how to serve his needs. Just remember that testing is a snapshot of your child: one test on one day. It doesn't change the person he is. The tests are a tool to help you serve his needs. Nothing more. They do not define him, and they can be wrong, so if testing doesn't reflect what you see, then don't take the results as gospel.
And BTW, before you even consider uprooting your child, I'd recommend that you find out if the SPECTRUM program is worth the trouble. If he would just be getting a 30-minute pullout twice a week or something, then it might not be worth changing schools for. It might be better to push your current school for other accomodations (grade skip(s), subject acceleration, curriculum compacting, etc.).
If SPECTRUM is a self-contained GT program, then it might be great!...or it might not work for your child. Every child is different. If you have a PG child and the SPECTRUM program is for "vanilla" GT or MG kids, then the program might not work for him, and sometimes GT programs are pretty inflexible about adapting. You might have better luck--believe it or not!--at a non-GT school.
I think at this point you ought to be formulating questions to ask. It seems like you can't get answers until you know what you don't know.
I'm going to be off the computer for most of the day, but maybe that gets you started? I hope!
K-