Glenntaj did a great job answering some of your questions. I'll add just a couple additional comments:

-Yes, the numb pinky toe, (and numbness in general) can be a symptom of SFN

-The general consensus seems to be that exercise is a good thing, to the extent that your body can handle it. "Exercise to tolerance" is a commonly used term. Everyone's body and condition are different. It's good to exercise, even if there is some nerve pain when you do it. But if it causes major flare ups, you may have to cut back or find a different form of exercise. I ride my bike outside or use the elliptical machine at the gym (vs walking or running) because it puts less impact on my feet and results in less discomfort both during and after