To start the diagnosis, look at the rear sockets. See if the ground wires plug into the sides of the sockets. I can't remember if that's just for the older round brass-base bulbs or if it's also for the newer flat plastic-base bulbs. Those ground wire terminals become corroded and can cause most of the symptoms you described. The high-mount brake light is a different story. He will have one or two smaller bulbs that commonly burn out. Failure of those bulbs is a lot more common than a failed brake light switch.