Long term use of Benzos like Klonopin may cause more PN problems than you think. When that drug wears off, there can be a rush of PN symptoms. This is because the Benzos are mild antiseizure drugs, and suppress pain signals. So those signals will bloom when the drug wears off.

There is a supplement called PharmaGaba made by PharmaGold (I bought mine on Amazon), which is affordable and works nicely but mildly on anxiety. I found for me it doesn't have to be used every day either once your take some for a week or so. I only use one when I need it. This type is better absorbed than other Gaba products. You might look into it.

http://www.nutrigoldinc.com/GABA

It is hard to say about the effects of your specific mutation.
But I do know that the higher your blood levels the more B12 will cross the blood brain barrier and get into the brain. Methyl B12 is used as a cofactor to make melatonin (the sleep hormone) from serotonin there. People with Fibro and MS have been tested and found to have very low B12 levels in the spinal fluid.

Neurological symptoms precede anemia in many people low in B12. It can take a while (several months) to fix damage. If the damage is longstanding, some may be permanent. You will want to take methylfolate too, and when you do-- try to avoid folic acid. Some new papers suggest a competition with both for crossing the blood brain barrier, and mention has been made to avoid folic acid to get the methylfolate to work better.