let's do some math here...
you knew each other when you were children. I presume that was quite some time ago.
you met again as adults. you live some distance apart and thus didn't really SEE each other in their daily lives, only in the times you got together.
you started dating roughly one year ago. since that time he finally revealed to you his problems with addiction - mind you he was drinking at the time. his drinking rapidly progressed and he wound up in hospital or detox 3 times in rapid succession. for the past SIX months he has been in a treatment type facility, even further removed from you.
the facts are you BARELY know this guy!!!! he has a bad history regarding his addiction and where it took him. once addiction is set in place it never goes away. EVER. at best it is placed in remission. and that takes monumental effort, every day. his history has demonstrated that he can NEVER again safely use drugs or alcohol. at all. as you have now witnessed any return to use escalates to dangerous levels.
he has a big mess to resolve - not only his own addictions but dysfunctional familial relationships, and a 9 year old daughter which we could only hope he strives to be a good father to. a good decent solid responsible dependable parent. he has a whole life to reconstruct.
in this short chaotic year you feel you have become emotionally and psychologically dependent upon him. and yet he's never really BEEN there. he's either been racing headlong on a path of destruction OR clawing his way out.