Hello befuddled, and Welcome to SR!
Your story is very familiar to us, but it is your story and you are welcome to share it here.
One thing I have learned is that an alcoholic will not change unless and until he (or she) is ready to do so themselves. If you had stayed with him, his behavior would likely have been more of the same.
There is a lot of great information at the top of this forum page (called stickies). I hope you will take a few minutes here and there to read through those--learning about alcoholism really helps even if a relationship has ended.
Welcome, again! Sorry for the reason, but I am glad you found us.