WARNING: WHAT FOLLOWS IS HARSH......
Whatever you do, DO NOT accept a bunch of promises from him to change everything and then go through with the wedding.
Keeping their addictions and abusive behaviors a secret is a big deal to addicts and alcoholics. He would promise to conquer death itself if you threatened to out him and his problems to the world. An empty threat just to manipulate him would just lead to a bunch of quacking. Just don't marry him. Don't threaten or talk about it or simper about it. Just cancel and and tell him why without discussion or he very likely will talk you into it anyway. Trust me on this one.
Do not have anything to do with this man until you see REAL, MEASUREABLE, SUSTAINED CHANGE. A YEAR OR TWO or more depending on your situation.
FH is a binge drinker and has been a binge drinker for the length of our relationship. He has been to counseling sessions and quit drinking for a month, but ended up losing his strenghth and started up again.
So...can't stay sober, even with professional help. Makes promises and breaks them. To the best of your knowledge, has always been this way and hasn't changed.
His words are I'm a grown man I can do what I want.
Then....belittling your concerns along with a big dollop of entitlement.
If he's not drinking then he will jump to smoking pot.
Followed by escalation to stronger substances when denied his true love.
He has an addictive personality and is immature.
Is this someone you want to be with for the rest of your life? And if children enter the picture - is this who you want for their father? An immature, self-righteous man who belittles your concerns? And when he does this in front of your children...or even to your children? What then?
Right now you are probably thinking....but what about all the money I've spent on the church? The dress? The invitations? And all the planning? What would people think?
Personally, I would rather they thought, "Whew - that was a close call for her. Good thing she got out in time" rather than "Poor thing - I feel so sorry for her, being married to a guy like that". Consider any money you might lose as a fee in the School of Life. Make sure your money goes to good use.
Take what you like and leave the rest.