Welcome to SR, Pegasus, I'm glad you joined us.
Sadly, they will use or not use no matter what we do or don't do. Our first step says "we admitted we were powerless over drugs/alcohol/others and our lives had become unmanageable"
I"m guessing that you have already figured out the "powerless" part, if like most of us you have tried everything to get him to quit. to no avail. If you tell him you are leaving (or that he is) he may go back out there or he may not....the thing is, you don't have the power of controlling his choice and if you decide to wait and stay, he may go out anyway...or he may find recovery regardless of what you do.
You can't love him into recovery either. If love could save our addicts, not one of us would be here.
It's okay to take a good look at your life and decide that you can no longer live like this. It's okay for you to find your own recovery and move on, even if he doesn't.
You have two small children and need to do what is best for them as well. Growing up in a home where active addiction exists is not healthy and often leads to repeat behaviour by the child.
Only you can decide what is right for you and your children. Just know that whatever you choose we are here to support you and walk beside you on your journey.
Hugs