Get used to the bullying. It will probably never stop. We were always told in nursing school that nursing is one of those professions that is known for "eating its young." I found that, going through my orientation with a seasoned veteran, could be challenging, but I never backed down and stood up for myself. However, my preceptor was always professional, which sounds like your preceptor was not.
Glad to hear that, overall, your meeting went well. During your med admin times, place yourself in a "No Distraction Zone." Focus on the task at hand, and don't let others pull you from that. We use this principle at our hospital, and believe me, it works.