Is this only for music, or tv shows as well? I find myself shuffling shows a lot and it was nice in Plex to have a smart playlist and exclude shows that had been played in the last X days from the playlist.

I just finished this book over the weekend. It was fun.

I went through this a bit ago. The calibration of your pace is set during an outdoor run. Try and do one or two outdoor runs at the same pace as the treadmill and it should adjust.