DS#2 (12, 7th gr) has similar scores and is 2E. He was also diagnosed with central auditory processing disorder, which affects his written expression. We have worked *hard* on punctuation this summer, and he still doesn't have it mastered.
As a school psychologist myself, I'm not sure I'd recommend you ask for more testing from the psych. I agree with the commenter that these index scores are more reliable and valid than individual test scores.
Both of my g/t sons had poor motor output at 8, and by 6th grade had better handwriting than their peers. So in one sense, I'd work with him on it but see if he doesn't develop out of it.
The relative weakness in memory, combined with the motor, can be tough for kids. I worked for a charter school in which practically every kid had this profile. I could imagine their neighborhood schools' teachers saying, "He's just lazy," or even, "He's average," while their parents said, "I know my child is smart!".
I am less opposed than I used to be to looking at ADD. Certainly I benefit from my 3 cups of coffee per day! I have been giving DS#2 a gingko/ginseng combination the last year or two.
Let me end with a HUGE endorsement of the helpfulness of a good occupational therapist. Evaluation and intervention.
Good luck with your smart guy!