Distinguishing "Presentations" and "Experience" in CV for application for Ph.D
How can I distinguish the two sections? Should I emphasize the content of the presentation more in the "presentation" section, and my day-to-day routine more in the "employment" section?

Answer #1) I would distinguish the two sections by calling one, "Presentation Experience". The ability to execute lengthy and quality presentations is a very valuable and rare capability. Not many people can do it well. I consider myself to be a poor presenter and I've personally witnessed people who present worse than I would. By all means, accentuate your presentation experience by providing as much context as possible. Let the reader feel like they can almost "see" the presentation as it took place.

Answer #2) I don't think it's detrimental if there is a little overlap between your job duties and your presentations. Simply don't provide much or any information about your presentations in your job duties section. You might mention that one of your current job duties is to make oral presentations as required/needed.