The idler pulleys are more common to produce noises when they're failing. The only noise that the alternator pulley will produce is a squeak when you shut off the engine.
No, I'm assuming the MK2 TT barrel is similar to a MK5 Golf. They're a bit more complicated and I've not taken one apart before. Sorry I couldn't be more helpful
I believe they're different, as Mk5 onwards had a different style of lock. I've never taken apart a Mk5 lock barrel though, so I can't confirm. Have you got a picture of your lock?