Hi Buxton and welcome. Does your fiancé want to quit or not? Does he want you to quit or not? These are questions you need to ask. A lot of partners will continue drinking and even sabotage our efforts because they don't want to lose a drinking partner or they don't want to have to examine their own consumption. They will drink in front of us or pick fights, knowing it is a trigger or is their excuse to continue drinking.
By now you have probably figured out that arguing over it isn't pushing him towards quitting and is only stressing you out. You cannot control what he does. You can only control your reactions to what he does. Focus on you and not him at this point. Get some sober time under your belt before you make any decisions. You need a clear head.
As for giving up. Well, I'm still with my husband despite the two of us cycling in and out of sobriety. He admits he has a problem and perhaps, at this point, his past experience staying sober is kicking in. But that is me. I've managed to stay sober through his relapse but I had to really let go. If he doesn't make it then I will have to decide. You may have to eventually have to make a choice. Do you really want to marry a man who is passed out drunk a lot, when you get home? If you plan to have kids, do you want a partner who is unreliable in minding children because he's passed out? You don't have to make that choice today. Just for today, choose to be kind too yourself and stay sober without any regard to what your fiancé is or isn't doing.
Keep coming back here and reading. There are a bunch of us on here who are alcoholics with alcoholic partners. It can be done. Just stick with your program.