Hi Nancy, my PN was caused through prediabetes & i was low in B12 but i am fine these days, my approach was low carb dieting and reducing the size of each meal & cutting out all sugary carbs like candy & other unhealthy snacks & no alcohol, there is no need for him to hurt whilst exercising, there was no way i could walk the pavements, it just hurt to much so i opted to go to our local all weather swimming pool and just walk up and down the lanes [ early in the morning when hardly anyone was there] even a lousy 30 minutes a day can make a huge differance in the long run, also a suitable muscel building program tailored to his personal health is a great way to get rid of excess glucose, it helps to unlock the insulin receptors, but just small steps at first building up slowly over time.
best of luck
Brian