I would also go with the kids angle... there are TONS of accounts about how divorce hurts children long term.

He is just thinking of himself here, and he needs to STOP that.

If you do have to confront him, go with the angle of the children, NOT on the angle of YOU, he isn't going to save his marriage for you right now... he MIGHT for his children.

He needs some marriage friendly advice that he trusts, and no one is offering him any...