Awesome movie with superb acting from all.

Rating: Null/10 (23 October 2006)

I truly enjoyed the movie and can't stop thinking about it. Could you good people help me with a few thoughts?
1) Someone told me that this movie was based on a true story, is this true, and do have any more information to share about the true story?
2) How does an Irish mob boss get the name of Frank Costello (why not Mcdonald, etc.)?
3) Who was the father of the pregnant girlfriend?
Thanks in advance for all comments.
ps One of the funniest moments for me was when Costello is leaving the diner and stops to talk to the 2 priests and nun that were sitting in the booth.