Hello dmmarch! Welcome, this forum is full with experience, strength and hope.
Make yourself at home.
What do I do?
What your gut and intuition tell you. It never fails. Never.
Will he ever change?
Alcoholism is chronic and progressive. He will always be an alcoholic.
In this forum there are alcoholic folks that have many years of sobriety though, so, its possible. However they have to take that decision and do it for themselves. Your partner does not seem ready yet. Maybe he is never ready- that depends on him 100%. Can you live with this uncertainty? can you live happy walking on eggshells?
I am very glad you are postponing the wedding. It is a very smart move. Why rush it? is it convenient for you to share finances, property, responsability with someone that cannot be trusted? hardly.
I really was heartbroken when an XABF (29) didn't remember anything. I went to live with him and noticed the extent of his alcoholism after months. I couldn't believe how different a sober him and a drunk him, were. By the end he told me he would drink until he died. That was 2 years ago. Today he still drinks and has a heavy drinker as a partner, too. And while I have mourned him, reading the stories here I am glad i did not marry or had kids with him.
And he made so many broken promises, I lost count.
In alcoholism you have to MUTE the person and see the actions. That is the truth.
Have you read the "classic reading" section in the Sticky part of the forum ?
Have you considered going to a therapist? interacting with an alcoholic takes a huge toll. It helps a lot, to have an ally whose goal is for you to be happy, and find out why you are attracted to someone chaotic and unstable. Often it has to do with our past and personal history.
Perhaps after he has 1 year of sobriety you can reconsider... ?
Welcome again.