Just a couple of thoughts.....

I would definitely go for the methyl form of folate and B12. Jarrow makes a good B complex using the bio-available forms. They also have a sublingual with B12, folate and B6. The p-5-p form of B6 is the better option and going with a low dose should be ok. Blood serum testing of vitamins is probably the least effective way to measure nutritional status. Unfortunately, many of the the other tests are not covered by insurance and can be quite expensive. My husband got more insights from an organic acid test and hair analysis from a highly qualified nutritional doctor but that too was out of pocket expenses.

With the B vitamins, B12 serum levels should be 400 and above. Also, they should have check your copper levels. There's a delicate balance of iron/zinc/copper. Low copper serum is associated with nerve damage and anemia.

How is your digestive system? There are links between gut health and nerves. H.pylori bacteria which causes ulcers can also contrite to problems outside of the GI track. Many have the bacteria without ulcers. Also, any medicines for acid reflux/GERD will impact your ability to absorb nutrients. The other GI issue that can wreak havoc on the nerves is Celiac/gluten intolerance.

Take care,
Marlene