i would go talk to the police officers' boss. maybe go to the mayor, first (if a city cop). set up an appointment, take some good people with you. be nice, but firm; that the situation was handled wrong. respectfully let him know, in front of your peeps, that the outcome was unacceptable. have the state statues printed out and in your hands....maybe even call the local news channel and see if they will send a news crew down with you; explain the situation to them, and tell them you are going to respectfully confront the chief about his officers protecting a vicious dog. nothing like a camera in the face to get results.
sounds like you have a good handle on everything else. good!
i have had great luck with that. police chiefs, and sheriffs, are public servants.