You need to get past that fear of calling for help...the hardest but ultimately the best thing I ever did for my H was dial 9-1-1.
I think it is time for you to own up...your not a failure...but you have a responsibility to you and your children...stop the drama and make sure he knows you mean business...the next time he makes a threat call the police...the next time he wigs out call for an ambulance...he needs help and you might be just the person to make sure he gets it...either way you need to protect yourself and your children...