The product you mention in your post...has benfotiamine and methylB12 in it. The benfotiamine is a low dose at 100mg.

That product is quite expensive, and today you could get both ingredients much less expensively. (the other Bs in that product are not high dose)

I'd get tested for Vitamin D levels and B12 and see what that shows.

There are many causes of neuropathy. Autoimmune, toxins, drugs (statins and fluroquinolone antibiotics among some less common drugs), hereditary, etc.

If you have a hereditary form, not much in the way of supplements will help.
If from drug toxicities, acetyl-l-carnitine may help.
Autoimmune is treated with RX IVIG infusions, and some immune suppressing drugs.
Poor circulation to the feet...peripheral artery disease should be evaluated.
Did you have chemo for the melanoma? Chemo can cause PN.

Are you gluten sensitive? Ever try the gluten free diet? This may help when other venues are closed.

These are just some ideas that come up on this board from the various posters.

PN is very complex and different from person to person.
Your back issues may be the main cause for you or you may have some mixed issues as well.