Hi Amanda and welcome. Have you tried Alanon? It can help you to understand your husband's problem and what role you play in it. It can also help you determine the best solution for and your children.
You asked why the old methods you used to convince your husband to stop drinking aren't working now, and here's my answer:
When your husband stopped drinking years ago, it wasn't because you begged and pleaded him to stop. It was because he'd finally realized on his own that alcohol was making his life miserable and that the only way out of his misery was to make a change.
Unfortunately, alcholism is a chronic disease, and it's prone to relapse. Your husband found himself using old behavior patterns to mask some other problem. That's why he began to drink again. And once an alcoholic resumes drinking, it's very difficult for them to stop.
It won't do any good to beg and plead with him to stop. It won't do any good to make him sleep in the garage. You can't make him change. You can't control his drinking, you can't change his behavior, and you didn't cause it. The only person you can change is yourself and how you react to his drinking. Your husband will only stop drinking when HE decides to stop. Will that happen? Perhaps. He's stopped successfully before. But then again, perhaps not.
You have to decide what's acceptable to you and your children and what behavior you're willing to live with today, tomorrow, next year. And Alanon is the best place to start.