Sorry to hear that your situation is not as responsive as one might like. Math enrichment can be challenging for elementary schools to manage (even though it should be easier, in some ways!), since "enrichment" in mathematics often involves grade advancement or cross-grade instruction.

I'm also wondering a bit about whether there are vulnerabilities in fine-motor skills or motor automaticity, given the history of suspected learning disabilities in writing, and the meltdown when asked to copy sentences. Behavior always means something. You may wish to investigate further evaluation by an occupational therapist. Also, while obviously you would have a better sense of the ASD diagnosis than I would, ASD-type presentation with writing/fine-motor challenges sometimes coexists or is a rule-out with other diagnoses, such as apraxias and dyspraxias. (BTW, how is his oral expression or dictated writing?) Especially since you mention early speech difficulties, which quite often are in the mix with dyspraxia. So also something that might be worth exploring--likely best done in a hospital/clinic evaluation.

Depending on your state of residence, you may be able to indicate that you are not satisfied that the evaluation addressed all areas of suspected disability, and request that the district contribute toward an independent evaluation. (Actually not that hard to establish, since they didn't fully evaluate writing.) Even if they do not, dyspraxia is a medical diagnosis, so evaluation of the non-academic portions may be covered at least partially by your health insurance, with a PCP referral.

...pronounced like the long vowel and first letter of the alphabet...