If I'm understanding right, your son's stronger language is not English.

I wouldn't re-test him again until you feel his English proficiency has caught up to age-peers who are native English speakers.

It doesn't seem unusual on this board to read about mathematically gifted children whose IQ is not as high as their achievement in math.

Right now, in your shoes, I'd focus my energy on finding an elementary school that can meet your son's academic and social needs.