1) It depends on how much is happening in the strip. A good estimate is 54-60 minutes. That's without scanning, photoshopping and PS2 breaks.
2) I used to have them done several days in advance but now I'm lucky if I make the deadline. Keenspace's system makes sure that the right comic is displayed on the right day.
3) I plan ahead on storylines (like the current one with cousin Chris was written in July) but I often make up the oneshots on the day of the deadline.
4) I have no interesting friends so a no on that. Eric is based on my cynical side though and cousin Chris is the very same Chriz from this forum. But even though my characters aren't directly based on real people I often use reality as inspiration.
5) I think I was killing nuns that evening. Or was it catholic schoolgirls? Hmm, I forget.