Last time I looked, there were 25 variants of the MTHFR mutation.
Some affect methylation at various points. Folic acid has to be methylated to work in the body. So does B12.

This chemistry is very complex. But today in US it is not common for people to be low in folate. That suggests a problem of some sort, because our foods are fortified with folic acid.

Typically when people have low B12 there is a corresponding low in folate. You have the reverse. While I am not an expert on methylation chemistry, I do think your test results are confusing. And yes you want MMA to be low to show B12 is reducing it in the body.

There is another way to test for nutrient status and it is believed to be more accurate than serum testing. It is called intracellular testing and reveals what is inside the cells and not just floating around the serum.

Here is one example:
http://www.spectracell.com/

Some of the newer holistic (also called integrative) doctors, chiros and naturopaths are testing this way.

I think you should explore what you see so far in your testing.
Elevated arsenic is a start. Going gluten free would be something you could do without spending more money on doctors.

Activated folate is available OTC as MetaFolin 800mcg by Solgar.