2. One could actually create a Playlist instead of manually building a list of files in Playing Now, and then one would never overwrite the contents accidentally, and one would always retain the full list of track desired for use at an event. One could even retain Playlist from previous events for replaying at a future date, which may be useful.
Also, Brian's suggestion would save you some of the time. The Recent Playing Now's are saved pretty often, although mostly on stopping and maybe starting playback, or when Playing Now is replaced. But also time-based I think. They do get automatically deleted after a while though, so I wouldn't completely rely on them.
1. That isn't MC doing that. I suspect that you are using System Volume, and that your mouse driver is set to change volume in Windows, which changes the System Volume, and hence the MC volume. Use Internal Volume in MC. It is better, and Volume Protection works as described in the Wiki.