Could the black, flaky spot be something sticky or "tar" like that is simply stuck in the fur? Is it a sore that keeps opening/draining causing it to scab over? Can you post a pic?
As for the eating habit of getting a kibble and running into the room and eating kibble by kibble in front of you, i think is "normal".
Mine Dudley does that and the past yorkie would do it too
I think it's cute.
hopefully you can post a pic and someone will be able to help out with the "black spot", good luck!