Can someone you love just have too many flaws?

Paul and I have known each other since we were eight years old. We are now 26 and 27 respectively. He was and is my twin brother's best friend. He was the first boy I ever kissed. He was also my first boyfriend. However, we are incredibly different. I've only had three boyfriends my entire life and each of them I've dated for several years at a time. I'm a very old-fashioned goody-two-shoes type. I'm a virgin by choice. I come from a very close, upper-middle class Catholic family. I received my Bachelor's degree from The University of Notre Dame and am now a marketing professional working towards a Masters degree. Paul has dated (and slept with) upwards of twenty women. He comes from a lower-middle class family. He is no longer on speaking terms with his father and one of his four brothers. In high school he fell in with the wrong crowd and while attending community college, got caught with a group of guys breaking into cars. He spent two years in jail and is currently serving a two year parole sentence. We got back together nearly six months ago and he respects my decision not to have sex before marriage, he respects my goals and my dreams and we love each other. However, the longer we date, the more I find out things I don't like. I've chosen to ignore his past as I know he's grown up a lot and would never do anything like it again. However, I have recently found out that he's a compulsive gambler. He loses and wins thousands of dollars at a time making bets. He also smokes and drinks. His father is an alcoholic and I worry he's headed down a similar path. He's a wonderful man, but the gambling, addition to the alcohol and the smoking (my uncle died of lung cancer from years of smoking) is really making me start to wonder. I know you are supposed to love unconditionally, in spite of all faults and I do, but these are big faults and I don't know if I can be with him with these major faults...what would you do if you were in my situation?