Should I even bother?

Hey guys, this is my first post here and I'm sorry its so long but here goes nothing. Ok so about a year ago i met this guy through a friend, we'll call him K. K was real nice to begin with. (For the record i HATE smoking and drinking). He smoked and drank "occasionally" according to him. He said that if we ever got together he would stop in respect to me. Hes black and I'm white so my parents were not all for it and i was scared of them getting angry so instead of inviting him over one day, i just snuck him over after they had left for work. We went a little too far that day (considering it was the first time we met), and we did some things we shouldnt have (too keep it clean, you get the idea, no intercourse though). After that he told me he loved me but then he didnt call me the next week. I was extremely mad cause i found out he had been out partying. We stopped talking for about 9 months and we met up one day and he told me he had stopped all that stuff and had re-enrolled in college and all that stuff. So he asked me out about a month later and we started dating. At first everything was fine; we both get jealous so we made a rule that he couldnt talk to other girls and i couldnt talk to other guys. He was always skeptical of me and talking to other guys (even though i kept my word and was faithful), he always got mad and flew off the handle for stupid stuff, but then i would see him texting girls all the time (it wasnt anything major, just like hey whats up, but still the fact that he said he wouldnt and did is disrespectful). Anyways about 3 months in, he just broke up with me over a text, blocked my #, blocked me on all social media and wouldnt even tell me what i did. So finally he called me and said he was sorry and that he was upset cause i liked a guys pic on Instagram (even though he likes girls pics all the time). And we got back together (even though i found out he had been smoking that night we broke up). Nothing was the same since then, he never payed attention to me anymore, was very distant, all that jazz. He had told me before he loved me and planned to marry me one day. And this time after we got back together, he left again a week later. He said he couldnt trust me, which i dont get because i havent done anything, he told me hated me and wanted nothing to do with me. Hes been smoking again and he started selling drugs again, and it really kills me inside to see him do this with his life. I really care about him and i dont want to see him mess up. I know i cant change him but i really need advice on how to handle it because it kills me inside to see him doing this stuff. Also, he came back to me today saying he misses me and that hes been depressed without me and he still loves me and wants to be with me eventually. I know i should let go because 1. He doesnt respect me. 2. He doesnt really care. 3. He has anger problems and flys off the handle but i cant. I really care about him and i dont know what to do. I feel like he traded me for drugs and it hurts a lot. Im not sure what to do from here... Help?

Dont walk RUN, this guy is going to cause you nothing but pain and heartache ,you're right hes not going to change and unless you want to spend your life as an abused woman thats if you get the guy which i hope you dont There are many men out there you can love ,take you time ,do interesting things and find someone worth having i wish you well but hope you get over this man...and fast.