I enjoyed reading your comparison of Jabba to Al Capone, and it made perfect sense up to a point, now forgive me if i'm wrong it has been a little while since I last watched Return of the Jedi, but doesn't Jabba say something to Luke along the lines of 'I've been hunting Jedi since before you were born!' now whether Jabba was boasting and bragging we'll never know unless he actually appears in Episode 3 hunting down Jedi as part of the Jedi purge. But it would make sense that he was more than just an up and coming thug at the time of A New Hope.

and from my limited knowledge of the EU, aren't the Hutt Clans meant to be quite established leaders in organised crime, it's quite likely that he was handed down the position, rather than worked his way up through the ranks.

I think it's pretty obvious in A New Hope, that Han Solo is almost too cocky for his own good (it's his personality) which is why he sass's Jabba and thinks he can get away with it.

Again this is just another point of view.