I would wonder if as an anesthesiologist...how much nitrous oxide you have been exposed to in the past 20 years? This is a huge risk factor for B12 metabolic failure.

What does one expect from the Mayo experience? A better diagnosis? ANY diagnosis? So you have small fiber...what will that tell you to do?

PN can be
hereditary
toxin induced (alcohol, occupational exposures)
drug induced (chemo, statins, HIV drugs, etc)
Chemically induced (solvents, nitrous oxide, etc)
nutritionally induced (low B12, and low thiamine, gluten intolerance)
autoimmune induced
rare disease connected (amyloidosis)
disease induced (hypothyroidism, prediabetes, paraneoplastic situations)

What is Mayo going to do for you that your own doctor cannot? Since you are a doctor yourself, you can get tests more easily than others posting here.

There is no miracle cure you know. The majority of the task is finding the correct diagnosis, for sometimes one CAN heal. However, the doctors will not offer healing to you...only drugs to suppress symptoms. Since Mayo Az....failed you, now you must take your own
case in hand and do it yourself. Like many of us here.

What kind of surgery did you have on your feet? I would start there.
But since you have had symptoms for 20 yrs? Thyroid, prediabetes, and occupational drug exposure should be your first stops, I would think.
Next up would be gluten intolerance/ B12 and MMA tests.

PN is a vast wasteland of wasted time, pain, and doctors who seem to not care much. When this happens people need to turn to support and other methods to find their answers. That is why there is an internet now.