My salt-induced flares subside within 12 hours or so. I try to drink a lot of water to help get the sodium out of my system, but it takes time.

Have you checked with a glucose monitor to see what your blood sugar does when you eat high carbs? A1c and Fasting Blood Glucose don't always show metabolic problems with sugar. Mine spikes horribly when I consume carbs, and there's no dispute that high blood sugar is an insult to nerves.

If you're not monitoring what happens to your blood sugar when you eat various food, you should consider it based on your symptoms. You can get glucose monitors really cheap (or even free). The strips are how they make money, but for just initial testing purposes, you don't need a lot.