Welcome to SR! Glad you found us. This stood out for me from your post...
Last year, my world fell apart when I received a call while on a business trip from my father in law. My husband was missing and he finally found him drunk on the side of the road, with his truck and towing our boat. I was devastated to say the least. I had NO inkling he was drinking again. fast forward to this year, he made empty promises, but I firmly told him I would not raise my children in an alcoholic household.
What happened to that resolve you had last year? That was the perfect response to what you were dealing with.
Whether he has hit his bottom or not, what you have been living with is causing you problems and heartache. Sure, when you threaten to leave, he says all the right things and makes promises and then you back down and he goes right back to the way he was. He is not more apt to seek help and recovery just because you are living there. If and when he decides he wants to live a sober life, he'll do it whether you are there or not.
Have you considered attending Al-anon meetings? You can learn a lot there and get face-to-face support from other people who are (or have been) in the same situation you are in.