1) Pike definitely captained the ship's maiden voyage, it is not known how involved he was prior to the trip to Vulcan. I suspect that he was the ship's first captain and that 2) Spock was his first XO. Remember, in this movie Enterprise is brand new, unlike the TV show where it was already a well traveled ship upon introduction.
3) Alot of people get confused on this, taking Pike's words literally. "For my dissertation I was assigned the USS Kelvin" A dissertation is a research project a college student does at either the end of their undergrad or grad level. It involves independent research and a report. His academic advisors assigned him to do a research project on the "Kelvin incident". It was not meant to be taken that Pike had actually been on the Kelvin during the incident, he was probably attending the academy.