i need a little insight

Rating: Null/10 (2 April 2005)

OK so...on the whole this movie was pretty bad ass. not having ever seen or read frank millers comics i got most of this movie. there's just some minor beefs i have with it and i think the might come from me never having read the comics.
who/what is josh hartnett's character? he appears in the very first and very last scenes as a killer but for whom? and why?
i wasn't sure if the stories were all supposed to be connected with each other or not because the only constant in them was shellie and the bar but then i read that its sort of pulp fictiony so that made it OK.
and this is the part part that bothered be the most (my spoilers in hear so i hope to god that no one who hasn't seen sin city reads this) Bruce Willis killing himself was totally pointless to me. i understand that it was a callback from the "an old man dies and a little girl lives" line from the beginning but him dying just to make that line fit was a bit much. if it was me and i was Rourke, Nancy would be dead anyway. if the one guy on earth i wanted to kill more than any other killed himself and i didn't get to do it and there's only one person left to take it out on (Nancy) shed be dead in 2 seconds. at least if he stayed alive he could have tried protecting her. that would have made more sense. but then i thought i might have been missing something from the comics.
so if anyone could clear up the josh hartnett thing and Bruce Willis offing himself id appreciate it. sorry if i ruined this for you.