Hello Justfedup.
Welcome to the recovery forum!
People have lots of reasons for staying. For some, the advantages of the relationship outweigh the problems. It's hard to see the dividing line, but it's a call that only you can make. I hope you will seek out an alanon group in your area. It helps to see that there are others going through the exact same thing and to hear their experience, strength and hope. It sounds like you are very close to your limit due to the effect he's already having on your children. I know some of the other moms will be along to tell you about their experiences. Since you can't be sure he will change, the only thing you can do is change the situation yourself.
Keep posting.
Hugs,
Smoke