Dont ever think of doing something so permanent, things will get better you dont have to kill anyone. Is there a way to ask your ex for help? You can always leave and come back to see your kids, or tell the police you fear for your life and that might have them check him more intensely. Just please dont talk like that I know what its like I think of it often myself but know that the feeling will pass, thats how I do it. Just go to the er is my best advice. Im worried about you, and know everthing will work out. But please get some help.