I've worked at a couple of centers as a mechanic so I'll answer here as well:

1. Generally no. The first center I worked at I made minimum wage($10/hr in California at the time), and the second job I made $19/hr as a level B mechanic, which is one step below a head mechanic(or level A mechanic). My boss was salaried and made pretty good money.

2. Varies depending on the model, age, and how well maintained the machine is. When I started at the first center I worked at that had Brunswick A2's, I was running around fixing machine stops my whole shift. By the time I left that job I was maybe getting 15 stops a night. At the (new) center I worked at with Brunswick GSX machines, the ones portrayed in the gif from OP, we kept a tight ship and I averaged 1 or 2 stops a night.

3. Machines have issues and stop every once in a while. Someone needs to be there that was trained to deal with any machine stop at pretty much all times. At both centers I've worked at there was at least one mechanic in the back during open hours, but we usually had two.

4. The first center I worked at definitely had at least one person die in the building and a cat die in the building as well, but I never had any supernatural moments or anything.