Lots of good words here. Most have suffered through years of misery with an alcoholic. The experience is there for you learn from or not. You have to choose. There is no magic pill.
Have you thought about going out with some other men? Perhaps some that might not have a drinking problem? It is a long distance relationship, you explained. You might find there is a whole different experience with someone who doesn't have a drinking problem.
My last pearl of wisdom: Don't marry this person without living with him for a while. Anyone, and especially an alcoholic can behave for "romantic weekends". But living day to day with one will be eye opening. And if you are not married, it will be far easier to pack your stuff and leave. Which you may discover is exactly what you want to do in less than a year.
Good luck.