E.,
I'm sorry that it seems you've gotten some unsolicited marital advice below... I speak from experience (coming from divorced parents myself) that I am actually better of for my parents having divorced. As long as you've explored all other options, you should feel confident in your decision. Most importantly, from here on out, make all decisions in the best interest of your kids. My paretns did an amazing job of never letting me feel as if the divorce was about me. And they NEVER fought in front of me. Now that I"m an adult, I can see that it was a little messy but they did everything in their power to keep that from me. And because of that, I had a great childhood, keeping strong bonds with both of my parents.
As for the kicking him out portion, definitely go after some legal advice. You need to be careful if he plans to file for custody. I think that if you kick him out and he wants to stay, he can use that against you in a custody battle. I just watched my sister in law go through something like this. Her ex filed for sole custody purely to get out of paying child support (he's not the worst dad in the world but definitely not worthy of full custody). He hired one of those lawyers that specialize in the man's side of divorce and his lawyer was a shark. My poor sister in law had to endure a ton. Another important thing is to DOCUMENT EVERYTHING. Keep a notebook of the time he spends with the kids vs. time out of the home and how he treats the kids including dates/times, etc. Be as detailed as possible. But make sure he can't find it. My sister in law did this and her ex (who was still living there during divorce proceedings) found her notebook and took it (then claimed he had no idea what she was talking about when she confronted him).
Anyway, best of luck and make sure to give those kids plenty of love through all of this - no matter how down you may feel. It will definitely pay off in the long run!