My 90 year-old dad has numb hands and feet, large nobby painful bumps on hands. Stubbed toe won't heal and is black. Won't go to doctor - ideas?

Get him in! Sores that turn black are of concern. He needs an evaluation.
See a physician. Anytime there is a wound that is not healing and the surrounding tissue is turning black it is imperative that this is evaluated immediately by a physician (urgent care, emergency room, foot specialist, primary care-whoever can see him first). The rest of the concerns can likely be addressed at that the same time.