(((hugs)))
First off. This is not your fault. You didn't cause his drug/alcohol problem. You can't control him. And you can't cure him.
I'm glad that you and your children are out of that environment. You should be proud of yourself for leaving. And there is no rush to go back either. His drug and alcohol problems are not going to get any better until something changes - him. And by his actions, it sure doesn't look like he's anywhere near ready. That means it's up to you to change the way you deal with him and his addiction.
You don't have to make any major decisions today - about staying or leaving. How about, just for today, you think about yourself and your kids, and what is the healthiest environment to be in. You don't need to worry about whether he's going to lose his job tomorrow, because, if he's going to lose it, you aren't going to be able to stop it from happening. Rushing back isn't going to fix the problem. But it could prolong it.
Take care of today. Take care of your immediately needs. And the rest will follow.
(((hugs))) I always ask myself, what is the WISE choice for the way things are right now. And then I go with it. Even if it feels uncomfortable. Trust yourself.