#1
If I were to want to be able to use a pre-prepared synth part off of my laptop, how do I keep it in time? There's an option to tap the tempo on the program, but that'd inhibit my ability to play other instruments. Is it possible to use a pedal to tap the tempo instead, so the pre-prepared part will stay in time with the other musicians?
#3
You're looking at it the wrong way round, you want to be putting your drummer on a metronome, so you're always in time with the synth.
#4
Normally the way to incorporate prerecorded parts into live performances is having everyone on click tracks. That's probably not an option for you. Is this a midi file you're playing through a VST?

It depends on how long your prerecorded part is, but your best bet is probably just practicing playing in time without a click track.