Fiancee wont take me back, She believes our relationship is toxic & that i have anger issues! Advice?

Im 25 and was with my ex fiancee for 6yrs, engaged for 2 but we broke up two years ago, She is 23 and we have known each other for 20yrs as our parents are friends. My brothers and i have earned ourselves a bad reputation but i cant say for what, And i would give my life to have my ex back. When we were together we were so happy and i loved having her living with me and waking up beside her everyday, But we had a toxic love. Although i loved her so much, I am easily pissed off and have a temper on me that if we where having a disagreement i would always shout at her, smash something against the wall or even punch the wall/door & if she'd try walk away from me i'd grip her arm knowing that i shouldn't have done that, Other times i'd call her a c*nt or speed in the car when she'd beg me to slow down, But when we weren't fighting we couldn't of been happier, I always told her how much im in love with her and wanted us to marry & start a family, We'd always have our hands on each other, snuggle and our sex life was unbelievable. I grew up in a home where violence was the answer to everything, I would never hurt her intentionally but she knew how to push my buttons and i'd always lose the head with her and it would kill me seeing her cry but we always made up and she'd call me a f*cking a*shole among others. Our friends always said he have a toxic relationship and don't know how we lasted as long as we did. 2yrs ago she broke up with me after one of our fights and she never took me back, I dated other girls and she stayed single, every girl i was with couldn't compare to my ex and even when i'd sleep with them i thought about her. I asked her to lunch yesterday and told her i wanted her to take me back and she told me that things are better as they are now and although she loves me to death she knows that us being together is not a good idea and thinks its best for us, As she was saying this she was teary eyed and im not giving up on her, She is the love of my life, It took years for her to finally agree to date me in the first place, I've had feeling for her since i was a kid, she always had me mesmerized by her & im willing to work on my faults i just cant imagine being without her for the rest of my life, Every time i see her i cant stop staring at her, Any advice?