I know your mind will be racing a mile a minute, but really, think about it, YOU have all the power here!
You know something that he thinks you don't. He's still being complacent. You know the score, and he has no idea.
Right now, the only person in the relationship that has any power is YOU. Use it.
If you confront him, you have the élément of surprise, and he's not planned for it.
He also doesn't think you'll do anything about it.
The only chance you have to turn a cheat around is to pull the rug from them, burst his bubble and take control.
Have him scrabbling for bags to sling a few bits in, and have to worry his arse about where to go at a moment's notice.
He doesn't get to take the car either. He has to lose everything.
Only then will he see what he's done.
You don't scream, you don't even raise your voice. You may get away with not even crying, you can do that when he's gone.
To have any chance of saving your marriage, you have to be clinical and decisive now.