I mean, I can’t just tell him to leave and pack up and be gone that day, can I?
Yes, you can. He's a grown man, he can book himself in a hotel for a few nights and either find a furnished apartment or a sober living environment to live in. One only need look. And you can do it in a kind, loving way. It's not about punishing him, it's about putting yourself in an optimum healthy environment. Keep the focus on you! *I say this from my own personal experience too. I've requested that my husband move out several times now. From my experiences, the calmer and kinder I was the easier it was on me.
I love my husband very much and living with him when he's going through a tough time with his sobriety is too much for me to handle. We need to live apart for my own best interests.
He has told me in the past that he will not leave, and that I will have to give him a thirty day notice, which I think is legally true?
I don't know about the legality of that, but if he wants to be difficult, that is his choice. Can you stay with family or a friend for those 30 days?
But I do think though, that as long as I do ensure that I don’t back down, don’t retract, and once he believes I am serious, he will want to leave, so I just need to make sure I am ready to stick with my decision when I make it.
You talk about him believing and wanting things. You cannot make him believe or want anything, you can only put yourself in the best possible scenario for yourself. He could very plausibly live the rest of his life thinking that YOU are making a mistake.