I am most struck by the notable relative weaknesses in visual spatial and working memory areas. Those two areas alone are probably responsible for his challenges in memorizing math facts. His scores are not generally average; they are quite diverse, ranging from Low Average (VMI) to Extremely High (WISC-V VCI), with scores in every category in between (Average, High Average, Very High). He has strong verbal comprehension, and good-but-not-exceptional fluid reasoning and processing speed. At this age, I suspect that his language strengths are enough to keep his math achievement up. His relative weakness in visual spatial may not affect his math achievement until he reaches geometry. Note that there is no measure of multiplication fluency, so the specific deficit that you report was not measured. Given his age, it probably would not have shown a normative deficit, but there might have been a personal relative weakness. Notice also that he did better with the procedural math than with math problem solving.
The working memory area can affect many different types of basic skills acquisition, including automaticity for math facts, phonetic decoding, handwriting, and spelling/mechanics. (It may or may not affect all of them.)
I would agree that there are a lot of ASD-type symptoms among the concerns you report, and that without a gold-standard ADOS-2, I would be reluctant to accept ruling-out ASD. I would also take the position that his testing supports something in the NVLD category, as he is relatively weak in exactly the cognitive area (visual spatial) most closely associated with the NVLD formulation. Insufficient academic testing was done to state that there is no learning disability. You have concerns about writing, but no measures of actual written expression were completed (he is too young for most of the WE subtests on the WIAT-III, but surely they had access to something else, like the KTEA-3 or WJIV; I would have liked to see a PAL-2). I find that many children with NVLD don't show early math deficits, but early reading or writing deficits, because primary level math is really a language activity, while early reading/writing skills are highly visual/symbolic. Later, in late elementary or middle school, sometimes as late as high school (at geometry/trig), it flips, when they've had enough practice with reading and writing for it to become automatic, and thus primarily a language task, while math becomes more about higher-level abstraction than basic skills.
The biggest tip-off that this is not just GT-ness is that he is distressed at school, not just by boredom or underchallenge, but by struggling to perform up to classroom standards in very specific skill areas.
You may wish to consider further assessment by a hospital/clinic-based team, who would be the most likely to have experience with an ADOS-2. Other members of the evaluation team that might be valuable may include a speech language pathologist and an occupational therapist. Depending on your insurance, you may be able to receive full or partial coverage for this with a referral from your primary care doc.
