1. What determines what a follower wears? Any way I can dictate this if I give them several pieces of armor?
2. What determines the weapon a follower uses? Any way I can dictate this?
3. Do followers level up? So if I give Faendal a greatsword, will his Two-Handed skill go up and eventually level up a new level?
4. Can followers permanently die? If so, what's a good way to keep them alive? Can they die if I tell them to go home (die on the way home)?
5. Any glitches or bugs to get more than 1 follower?

This should answer your questions.

http://www.uesp.net/wiki/Skyrim:Follower

There are ways to get several followers. i do not know if they have been patched, as of late.