Can I change the time increment from 15 minutes to something else?
Yes, individual users can change this on the fly on the "Settings" tab in the calendar's left hand sidebar.
Administrators can change the default time scale in Admin Settings / Time Scales.
How can I see more all-day events at the top of the screen?
Users can't change this on the fly, but as an administrator you can decide on the maximum number of all day events you'll show before showing "X more" and forcing users to switch to one of the list views. You'll find this setting on Admin Settings / Views as "Maximum all day rows to show".