I would certainly keep exploring the nutritional issues especially since your tests show a folate and iron issues. Drugs deplete nutrients and if your nutritional status was suspect when you started the Flagyl, then it doesn't take much to push things over the edge. I would also assume that there are other nutritional insufficiencies contributing to it. Most docs don't consider a low normal reading of a nutrient an issue but should. Make sure to get copies of all your lab work. You'd be surprised at what they miss or don't tell you.

Flagyl can deplete B12 and K. What was your B12 level? A low normal reading on this should not be considered OK. Also, all nutrients should be stopped prior to testing in order to get a better reading.

What are you taking now? Key PN nutrients are the B vitamins( especially B12, folate, B1 and B6), Omega 3, magnesium and D. R-lipoic acid, Acetyl-carnitine, and NAC can be helpful to heal damage from drugs. Healing nerves can take a long time but at least you are on the right path.