The MTHFR mutation is very common in auties, which it sounds like, and it leads to B12 deficiency which causes allllll kinds of psychiatric issues. (It almost killed me, luckily the dizziness triggered a naturopath to test me)

If I were you, I'd start taking No Shot methylcobalamin (NOT cyanocobalamin!!) as it's water soluble so you'll just whizz it out if you don't need it. If you do, you should start seeing changes on the first bottle. (If you get tested first, they need to check the homocysteine levels as well as the MMA, + they almost never do that)

I hope that's helpful and not just a random info dump!