Trying to control a drunk (in my case - my dad) is an impossibility - wasted effort.
Having grown into an alkie myself, I can say with confidence NO amount of pushing, encouraging, threatening, etc mattered much to me....... until it mattered to me. I had to come to that decision on my own.
That said, your mom's drinking and her lifestyle are up to her to continue or change. What's usually best is to stay out of it and be a role model for what a healthy relationship looks like. Perhaps you can recommend to your dad that he move on himself but there again, that's his choice to make and one he'll have to weigh the pros and cons of.
If you want to hear from some folks with real experience in this sort of matter, I'd HIGHLY recommend asking some of the folks in the Alanon area of SR (
https://www.soberrecovery.com/forums...riends-family/) or maybe the ppl in the friends/family area of SR (
https://www.soberrecovery.com/forums...ly-alcoholics/)