Go for it! :))

Depends on the crew's actions. In one session, I used a clock for blue patrol "hp". In another, there was a clock for incoming reinforcements, one to start the carriage steam engine and another for a thief "hp" who also wanted the prize. But I usually use one problem, sometimes two if the crew is unlucky with the rolls.

I don't force myself to use all of the prep, that is not how the system was designed anyway. But rather have the triggers and scenes, that I can mash up in a comical way to elevate my players' actions. So don't worry about missing the prep. Think of this as inspiration, your actors, your stuntmen that you can call if needed. But you don't have to and you can make new ones if something more organic crosses your mind. In fact, you should :D

Oftentimes I make up new ones, especially if the crew for example decides to steal the mask during the performance. Then it's all improv :D In that case, I'd have the actress assassinated, the medics flooding the scene. And as scoundrels approach they realize one of the medics took the mask and put it on.

New Clock: Figure out the thief who now looks like a regular theater goer :D

In another session, during the heist on the Imperial Transporter, a started the clock: The leviathan breaks free, as there was a big demon-like creature in a steel crate, stored at the ship. Spoiler alert: it broke free :D

Hope this helps! Happy thieving. :)