Hi. I am the parent of an almost 11 year old son with motor dyspraxia and sensory issues. I remember reading some of your posts and thinking your son sounded similar to mine.
I have homeschooled my son since he finished Kindergarten because the Kindergarten teacher thought he should go to a transitional first grade (a year in between kindergarten and first grade) the next year so he could learn to color in the lines better. She didn't think he needed to learn anything at all the next year. I talked to a first grade teacher and mom of gifted sons and showed her samples of my son's work and asked for her advice. She was working on a degree in special ed at the time. She told me I would need to homeschool my son because she believed he was most likely highly gifted and he would not get the education he needed at that school. She made it sound like it would almost be child abuse to let him continue going to that school. Because my son was reading at about a 5th grade level when he started Kindergarten at age 5 and doing some multiplication and division, he was not eligible for OT for his handwriting issues. Children have to be at a point where they are failing before they are eligible for help with a disability and he was able to work above grade level in everything except those things requiring good motor skills. We explained to his teacher that he had hypotonia, which is all we knew that he had at the time, and it didn't make a difference. There are no exceptions to the rules. Children like mine are discriminated against and not given help for disabilities if they are too smart and that is just the way it is and I had to accept it.
I homeschooled for a year and let him do math mostly with computer games and I think he looked at a math dictionary that I actually bought for me because I was afraid I might have forgotten a few things. When he took the WIAT the month he turned seven and should have just finished first grade he tested at a fourth grade level and the educational psychologist told me he thought he could have gone higher if he would have used a pencil and paper to figure out the answers, but he refused and he was getting tired. After that test I let him use fourth grade math materials and he was actually able to do just fine with fourth grade math except I had to let him do fewer problems because of his handwriting issues. One multi-digit multiplication or division problem would take up a whole page. Luckily they didn't test his coloring or shoe tying abilities. They did test his spelling by having him write the words. He could have kept going if his hands hadn't started hurting but I guess there are no accommodations for that kind of thing on the WIAT. He only tested slightly above grade level in spelling because his hands got tired, but I know he could have tested much higher if they had let him continue orally.
My son is doing 8th grade math now and he rarely makes errors. I finally let him use the calculator more this year and this really helps him. He still uses a lot of mental math though because it is sometimes faster for him than keying in the numbers on the calculator. He only writes what he absolutely has to and I am sometimes amazed at how little he writes and still comes up with the correct answer. But if he were in our public school they would say he is not gifted in math because he would take twice as long to do a math worksheet as other kids because of handwriting issues and they would not let him work at his level.
My son's vocabulary and comprehension and general knowledge seem to be at a higher level than his math ability, and people have told us for years that he talks like an adult. I don't think my son is as gifted in math as he is in other things but I still think he is gifted in math no matter what anyone else says. He just has to work around his handwriting issues and this might make him appear to be slower in math if he is required to show his work and do a lot of writing. When he is allowed to compensate by doing math his way, he is able to do so much more.
