The black ear wax is residual mites - just keep cleaning them out with damp tissues or proprietary ear cleaning pads. I had this problem with one of my kitties on first acquisition and was told to clean them regularly. It's amazing how far down a kitty ear'ole you can get a tissue-wrapped pinky finger!

Good luck with him... once you've sorted out his diet, I'm sure he'll be a credit. Remember, kitties have food allergies just like people so if he does well on plain rice and chicken, introduce new foods gradually and keep a diary of what you put into him and what came out... you'll be able to work out what it is disagrees with him.

LTS