There's something in preferences in ableton under Audio I believe where you choose between the computer's outputs and other pieces of hardware, I believe ableton recognizes them based on drivers. Should be a little drop down bar saying something like "M-audio USB" If it's not showing up in...

Terms like verse, chorus, bridge, intro, etc, are mainly subjective, and mean something different to everyone. However, in my experience, the purpose of a bridge is where it gets its namesake. The bridge is meant to BRIDGE two sections of a song. Use it as a smooth transfer between verses, choruses,...

Unless you have pro tools 9, i'm afraid you're stuck with digidesign or M-audio hardware, depending on your version.
Digidesign just liked to be sizan pre pt9 that way...

Well, if you're actually DJing and mixing on the spot at said parties, you'd want a DJ mixer. 2-4 channels, crossfader, etc...
If you're just playing tracks... get an ipod.

My main rule when producing is that if you add something to the track, mute it, and it didn't make the track sound any worse, then you don't really need it, do you?
K.I.S.S.
Keep it simple, stupid