Small brown patches on the skin of your legs indicate the beginning of a superficial ulceration which may eventually become infected. Bullous diabeticorum is a blister that appears without injury. You should immediately lance it with a clean needle and remove all the fluid from the blister immediately. Ingrown toenail, even if it's infected, as long as there is no pain, should be left alone. To prevent blood under the toenail, you should wear shoes that are one size larger and wider than your actual shoe size.
Prevention is much less costly than the treatment.
People with flatfeet are prone to develop a diabetic Charcot's foot. A Charcot's foot is a common cause of leg amputation in diabetes. You can always tell if you have a bone infection in your foot by looking at the x-rays of your foot. There are no medications for the treatment of diabetic neuropathies. You should minimize walking and elevate your feet as much as you can.