I'd look first at the Country Life product. The ones I found online all had magnesium oxide in them. When that happens, when companies MIX different types together what you really get is mostly OXIDE... this is because the oxide is cheap and has a chemical make up that allows for the company to "claim" presence of it in high amounts. But what REALLY happens is that Magnesium in oxide form doesn't get absorbed much at all.
I called two companies a couple years ago on their consumer number, and they could NOT tell me how much magnesium oxide was in their product from their information sheets.

Magnesium chelates make for very large tablets, and oxide being concentrated, is handy to keep the size down. So it is often listed on ingredient labels. To get the benefits of magnesium you need to use a chelate separately (or a powder form listing no oxide).. magnesium is critical for many processes in the body and making sure yours is absorbed is important.

You might want to add in antioxidants, either by food choices, or supplements. Grapeseed extract, or a more potent curcumin source (your Tumeric product may not be optimum because curcumin is poorly absorbed), or astaxanthin (a carotenoid from red algae which is popular now). You can start with one of these, and change or add as you like.
I've used grapeseed extract with great success for years for allergy at 200mg a day. There are many other antioxidants that help too. Foods like blueberries and green tea are good food choices.

Here is an example of a stronger curcumin:
http://www.epic4health.com/cuul500mgena.html

I don't see any omega-3's on your list. Please consider taking some of these also, as they help with nerve maintenance and repair. You can try fish oil daily or Krill oil if you don't eat salmon at least once a week.

PN's progress for two basic reasons. Either you are intolerant of something you eat or take continually, or you have an hereditary genetic neuropathy like CMT.
So examining your food preferences, and any drugs you may be taking is important. Exposure at work or home to chemicals like outgassing formaldehyde, or ant poisons, toxic molds, etc need to be discovered.

But most commonly it is food that can be implicated in progressing cases, with drug use following close behind.