Presenting = stepping onto the mound with the ball in the throwing hand, not in the glove.
I have no idea what the walking to the back of the circle violation was either - he called it on the other team, so I only heard his call from the field, and not the explanation he gave the pitcher.
The pause - I talked to our pitcher about that. She said she does it on purpose once in a while because she feels she gets a bit more speed out of it. Basically she steps on the rubber and goes, she feels it gives her a little more (like a walk-on) but watching her, there is really no difference. She is just hurrying the pitch.