Just curious. What happens if you take the kids and relocate to a state with friendlier rules towards dads? Where would the custody hearings take place?
In the USA, residency regarding custody is standardized at 6 months. So if he moved with the kids then she could have up to 6 months to file in the current county and likely it would take charge of the case.
I've been thinking... .If there is another incident then call the police again. Even if they sit on their hands and decline to do anything, you still have the option to turn to the court for it to step in. Just because the police fail to turn it over to a court or prosecutor, you can still ask for protection for yourself and children from domestic court. (Many courts are like my county which deferred protection petitions for the children to domestic or family court.) And since you called the police there ought to be a record of the incident, though you can't be sure in advance how favorable or unfavorable it would be, whether you're the one harassed or whether you appeared the problem person. At the least there ought to be a recording of the 911 call where you would be asking for help and her raging or banging in the background. Hmm, have you tried to get copies of your past 911 calls? If not, request them before they get discarded or the storage 'recycled'.