What you described sounds very similar to my pain.
My guess they are going to used the MRI to determine how much of your pain is from your lower back (L3-4-5) and how much is from your nueropathy.

In my case I have had numerous epidurals for the pain from my back. Luckily these have given me much needed relief. I'm down to only having a shot less than twice a year.

My feet still burn & tingle but the electrical shocks and zaps you mentioned seem to be most when my back is at its worst.

I have tried a TENS unit at times to help, it seems like it provides me some relief. I try to use the serious pain meds (Percocet) only as a last resort.

Good Luck