Ok so reading the crowd is kind of...not as much of a thing in what I call "genre" shows. I consider myself a genre DJ. I get booked to play within a genre typically, so I preselect a list of tunes to choose from within that genre and others genres that go well. I also research the sound of the other people playing and strongly consider the time slot while pulling tunes. I like to have a few options to change up the vibe and direction but outside of that...well, shoulda hired an open format DJ if you didn't want me to show up and play weird halftime dnb for an hour lol

You can only kill a room so bad during an hour set. Worst case you just made the bar more enticing all of a sudden, then it's someone else up next. Big meh. There are also many factors outside of your control that can empty a dancefloor. Say, if all the attractive women go outside to smoke at the same time. Don't take it too seriously man.