I'd probably expect to see a much lower comprehension score in a child with PDD-NOS or asperger's in that it is testing understanding of appropriate social responses and norms. Other than the low PSI index and block design, both of which can be explained by his hypotonia, honestly his scores look to me like a bright child and not necessarily indicative of anything terribly askew.
If we assume that those three low scores would have been more in line with his other scores were it not for that disability, he'd have FSIQ right in line with his GAI (low 120s), which is a kid in the top 10%.
I know that it varies from place to place as to what gifted programs serve, but I'd say that a kid in the top 10% is often a high achieving student who does well in GT classes, but who does not need extreme interventions such as grade skipping, for instance.
I wouldn't be surprised if your son is not treated as a top student or offered enrichment such as GT pull-outs due to his disability holding him back from performing the way others with his ability may. I wouldn't be overall concerned with the WISC or WIAT scores and they do line up pretty well with one another. I'd be more concerned with finding a way to get the school to accommodate his physical weaknesses such that he can participate in appropriately challenging classes.
