Hi Lynn, idiopathic???? prediabetes can cause the exact same symptoms as a full blown diabetic, mine was caused because of prediabetes, any neuro that is up to date should know this.
I am curious, how was you tested for elavated blood sugars ? you might want to check your vitamin levels as well, i was low in B12 as well.
Stress & the weather can aggravate symptoms, regarding the weakness in limbs, do you use statins for cholestrol ? as they can cause awfull side affects like that, good that your on a low carb diet already, any type of exercise you can manage will help the insulin resistance as well.

Brian