Your son is twice exceptional. Are you concern about
IQ test or state and classroom exams.Is your son on a IEP? If he is maybe you could request extended time on test as a accomodation.

Can the psychologist tell you his GAI score? I have heard that for a child that scores low in memory and or processing the GAI will give a better idea of his/ her potential.

IMO I think perfectionism can keep a child from performing on everything,sometimes even games. Also look into getting him help for his
anxiety issues.