Okay Lanny....

First off, you have to have good kidney functions to take supplements. But if you tolerate Lyrica with no problems, which is excreted whole via the kidneys, I suspect your doctor is monitoring that?

Secondly, anyone on Methadone needs to be watchful for potassium and magnesium levels. Potassium can be lost suddenly if you get diarrhea, flu, etc. Magnesium can be depleted by diuretics or heavy coffee consumption, or undiagnosed diabetes. If these two electrolytes fall, then the heart may start with long QT and go into arrhythmias. So choose high potassium containing foods to get that mineral, and do a conservative 1/2 RDA magnesium supplement.
Both help with other things, so this is not just for the Methadone.

Since you were taking two drugs that damage the nerves and mitochondria, it would be a good idea to try acetyl-l-carnitine and CoQ-10. The CoQ-10 is depleted by Zocor (statins).
Start the carnitine at 500mg a day or so and increase as needed to about 2 grams. Take higher doses in divided doses because this nutrient is not absorbed well. Spacing it out gives better results than one big dose.
CoQ-10 should be at least 300mg a day, in a form that claims to have enhanced absorption. Without help this supplement is not well absorbed either.

I'd also take 100mg r-lipoic acid. This works with the carnitine in the mitochondria to help energy production and control blood sugars some. Carnitine and lipoic acid are in some anti-aging products now, but they also help with damage that is present.

Keep with the B12. Keep that level up there. NIH recommends a B12 supplement for all Americans over 50 anyway.

There are some concerns about taking high dose thiamine when cancer is present. Here is one article explaining that:
http://www.benfotiamine.org/excessthiamine.htm
At the end of the article is a note, that studies in humans have not shown this to be true.
So use of benfotiamine for you would be your decision, considering the prostate issue. Dose range would be 300mg to start, which can be lowered after improvements to 150mg daily for some people. The controversy about thiamine/cancer has not been resolved, so even though there is far more evidence of benefit, since you have had that surgery, you would have to read the article and ask your doctor about it. If you only have BPH and no cancer, then that would not be an issue for you.
Benfotiamine is helpful for people with a history of alcohol consumption. I hope you are NOT drinking currently with that Cymbalta. This is dangerous for the liver.

I would wonder if your smoking has affected your peripheral arteries and is reducing the blood flow to your feet. You can have this checked at your doctors. Typically doctors will treat PAD (peripheral artery disease) and if you have this, improving the circulation to your feet may help the PN.

You can take a regular high potency multi vit with C and B's.
Choose one with zinc included. Zinc is important for males.

Also I would avoid foods with the commercial additive MSG. This really can set off burning and pain. I know when I have it, usually from some carry out or restaurant, it will flare me up for a couple of days at least. I am fairly okay when I am vigilant about it. MSG is in alot of soups, gravy mixes, boullion, etc.
Some believe that B6 intake helps with MSG, but I have not found that to work for me.

Today my feet acted up from walking too much and trying on a zillion shoes some of which squeezed them etc. So even tho I have them under control, I do have bad days still.
I ended up with a Men's New Balance athletic for the width. Right now they have recovered, but earlier today... zowie!
The new cushioned Dr. Scholl's slip ons are nice too. I am glad I checked the men's section--or I would have missed these!

Ask questions, if I have left anything out... I'll be here for one more week.