Only you know what is best for you. Not us here at SR, not your family, not the people in your culture. Only you, YOU have to live your life, walk in your shoes. Just you. And if you can't...or aren't sure, then you really should wait til you can... or are sure. Period. What would these same people think if they knew he had this issue, would they still think you should marry him anyway? Hmm. Would they want to be married to an alcoholic and all that it carries with it? Do you KNOW what happens to many families of alcoholics?
Its GREAT that he recognizes that he has a problem. That is just a huge bonus, because so many don't. Ever. But, how sincere are his words that he recognizes it, I don't know, I am not there to hear them. I can only, all of us here can only speak from our own personal experience.
I would hold off on the wedding. My gut instinct says RUN (I am SO GLAD I DID), because of so many reasons...and yet since I don't know your situation that just isn't fair for me to make such a huge all encompassing life altering decision for you. Honestly? It sounds like you already know what you want to do...you just want us to tell you we agree, that its ok, that its the right choice. And hey, I GET that. I understand.
You are so young. You have TIME, loads of time, to get this figured out. Money is only money, but your life, your future children, your whole existence depends on this massive decision, so its one that should be made carefully. Very Very Very carefully. Take time, pleeenty of time, to think this through.
Learn, read, talk to people. Educate yourself in this as much as you can. If your gut says wait, then you should wait. Alcoholism is progressive. It gets worse. In myriad ways. If its bad enough now that he is going to rehab, there is a very good chance that he will relapse afterwards and get even worse because you don't get to rehab by drinking two beers once a week..ok I guess you could, but you get my point. Its just the truth. Of course, he might not, he might beat it and get sober. The odds are stacked pretty heavily against that though aren't they? I would much rather you hear the hurtful reality of it now than later.
Doing some math here, you have been with him since you were 17...basically your whole adult...I say adult lightly, not rudely, but hey, you are so young...your whole adult life. Have you had any opportunity to see other guys? To date normal guys, by normal I mean sober. This would definitely put some perspective on this guy.
You only owe yourself an explanation. So hey do some deep thinking. The wedding isn't tomorrow, its months away. For your sakes, for the sakes of your future kids, please please think this one through as carefully as possible. Their lives will absolutely be impacted by his behavior....whether its good or bad, ok? And his behavior will affect them...to the point that it affects their parenting skills...and then their kids.
I have seen this in my ex father in law...and I had no idea what an ACOA was until I got here. Had I known...I would not have married my ex husband, who won't touch alcohol but has every behavior of a dry drunk co alcoholic. My son was learning those behaviors til I divorced his verbally/emotionally abusive dad and booted him out the door. My ex father in law was an alcoholic who got sober when his wife presented him with divorce papers. His dad was an alcoholic, and his dad and so on and so forth. It perpetuates in the generations in untold ways. My kids are now watching what used to be their 6' 3" grandfather barely able to walk, because he has so much damage from decades of a twelve pack a night. They have moments where he makes them cry because of his dry drunk ******** behavior...and they watch him fade into nothing, decades later, because he chose to drink like a fish every night. Probably to cope with his memories of growing up with...yep, an alcoholic. Dummy me, I jumped out of the fire into the pot or however that goes? I left my ex husband, and found myself a mentally unstable abusive alcoholic. Aren't I brilliant?? He started out perfect, it felt perfect....but now, years later, years that I cannot get back, my kids are damaged from watching their mom get hurt and abused, my kids are fighting some of that learned behavior themselves. I am damaged, as well. They have to watch me try to pick myself up and put myself back together. If I could go back to that one moment where I had that choice...much as you have that choice now? For my kids sakes? I would boot myself in the ass and say OH HELL NO YOU DON'T. I would tell myself to get the hell away from him. There are millions of men. Ya know? So, hey....THINK this through.
Hugs. And do not let anyone tell you how to live your life. Ever.