married
This is just my thought: if you established the date for filing and don't follow through he will see it for an empty threat. Further, you are not responsible for the relationship he will have with his children after the divorce. That is for him to work on. Kids see and hear AND understand more than we give them credit for. They might be angry at you for a while, but you will forge through that and have a wonderful relationship with them due to YOUR efforts to do so.
You deserve better than what you have. So do your children. JMHO.