my ex [30M] just moved back to town [23F] and I'm struggling

Bit of a long story guys, so thanks to anyone who makes it to the end and can offer some insight <3 My ex and I (let's call him NV) started dating in the July of 2014. We were both servers in an upscale restaurant, and we hit it off right away. We got very serious very quickly, and were very committed to each other. In November I found a half empty bottle of vodka hidden in his couch. I was devastated because a) we had begun our relationship with me saying flat out "if you drinking excessively is who you are, so be it, but tell me now cause I don't wanna get involved with an alcoholic" (he thought it over, and decided to cut back his drinking), and b) because of my past history with alcoholics in my family, I knew what staying with an addict looked like. We had a fight about it, and I chose to end it the next morning. The next day rolls around, and he sent me a long message professing that he could now admit to himself that he was an addict, that abstinence was the only way for him (he's tried rehab, cutting back, AA, etc.) and that he was going to change. I chose to give him the benefit of the doubt because I love him and wanted to help him. He was doing great until Christmas rolled around. He admitted he was scared of what his family might think of him not drinking (they're all pretty big social drinkers) and I caved. We decided to shelve the sobriety until the new year, and he promised to stick to beer/wine over the holidays. Fast forward to March, where in the course of 2 weeks he went MIA on me twice; once for a day, and the second time for 4-5 days. We always kept in contact throughout the day, so when he went missing the second time, I was terrified. I contacted his brother, who called his parents and they found NV shut in his apartment, crying and disoriented. At this point, he agreed to go to once a week group counselling. This seemed to be having a really positive affect on NV: he was more open in his communication with me, he was more productive with his time, he was enjoying the gym more, etc. In April, I got a job at a new restaurant and that's when things seemed to take a turn for the worse. My hours were longer and our days off didn't always match up, so it became more difficult to see each other. My new coworkers partied harder than anyone I'd ever seen (really not ok stuff-won't get into it here but I'm sure you can imagine), and eventually, some of them approached me saying they'd seen NV out drinking with some friends on various nights. Being the new girl, I felt that they really had no reason to lie to me, they were just trying to make small talk (no one knew he wasn't meant to be drinking). I chose to give him the benefit of the doubt. Eventually, one too many of these stories came up and I had this horrible gut feeling, so I went through his phone (not excusable I know, trust me I've been harbouring enough guilt on that note for a while) and found messages between NV and an old coworker of ours about them getting drunk. I was so heartbroken. He admitted that he felt I was the only thing that motivated him to be sober, and he felt he was "hanging by a thread all the time". I wanted so much to help, but I felt there was nothing else I could do to help if he couldn't help himself. We broke things off and we ended our contact by him saying "I can't put effort into our relationship if I can't keep myself together. Give me some time". So I did. In September, he'd posted on FB that he was moving away. I reached out to him because I wanted to see him before he left. He always agreed, but when the day came, there was always a reason for him not to meet me face to face. 2 weeks before his flight out, he revealed to me that his drinking really spiralled out of control and he started taking excessive amounts of Xanax on top(and probably cocaine as well). Immediately, I contacted his brother (they're very close) and told him what I knew. The brother had just been in town and had barely seen NV because of excuses like "sorry man, I'm doing double shifts at work this week". The brother didn't know NV had actually been fired for being overwhelmingly intoxicated and insubordinate on the job the week before. He came back to town a few days later, and we went over to confront NV and try to get him help. He didn't want it, and he left a few days later. What I'm getting at with all of this is I'm still having a really hard time not being with him. Having read many posts/blogs/books/articles on addiction and alcoholism, I feel I understand the nature of the condition better, but it doesn't help with the pain of being without the man I love. He was never abusive in any way, was always the most loving towards his family and me, and has the most wonderful character of anyone I've ever known. How do I cope/move forward knowing he's chosen addiction?