Do you blame using on anyone but yourself? Because his drinking hard, that has absolutely fuck all to do with you. Perhaps your mutual circumstances accelerated his problem, but him 'picking up a hella drinking probs' (is that English, now? The flexibility of language is quite incredible) is all to do with how he handled circumstance, not you. Addiction isn't leprosy.
It sounds like he was a mess as well. And it doesn't sound like he left because you were one. It sounds like he was fucked up himself.
I left because I didn't want to get into the messy tangle of emotions that inevitably comes with being with someone. I didn't want to know somebody else's family. I didn't want to meet her parents, or to fund her brother's mistake, or to worry about paint color on walls, or whether the sink needed fixing. I wanted the bubble, which is an unrealistic ambition in the best of times.
Honestly I think imagining someone is set to leave any moment is probably exhausting, rather than adding spice to a relationship. If he's been married before, he's signed up to commitment. Being willing doesn't mean it always works out. You can't live, waiting for someone to leave you. You want him to believe in it, you need to believe in it.
If I 'legit care' about someone and they 'legit care' about me, either it's still too good or not good enough. Besides, loneliness can be dealt with so long as you've got enough money to throw at it. And I'm not lonely enough to want to put myself on this particular cliff-edge, thanks.