I'm guessing this woman he will marry is younger than him and probably vulnerable to his white face and foreign passport, so she is with him even though he's a drunk and maybe will be abusive to her one day (if he's not already).
I am very curious him why he was always drunk when relevant the marriage? Marriage means a man has to grow up hence why some men are afraid of commitment and stay single.
You must know that many American people have some type of addiction in their live. Using the Alcohol to correct problems( doesn't really work) is his way of dealiong with issuses.
Alcohol/drugs/sex/food/ traveling/ just to name some. And gives a "black-eye " to your company that he works at.
He obviously does not want to get married and still does seemingly because he has a desire to get married but, that doesn't mean he is 1. And once married, that need still remains and starts the whole cycle over again.
It would appear that your friend has many problems beyond the normal "wedding jitters", and is using alcohol to try to correct the differance.