A Brooklyn mental hospital is a violence-wracked, dangerous place, rife with assaults and at least two deaths linked to paperwork snafus, the Daily News has learned. Federal surveys and court documents paint a disturbing portrait at the state’s problem-plagued Kingsboro Psychiatric Center. “Violence has become a way of life at KPC,” an independent mental health expert wrote in a Kingsboro-commissioned 2009 report after the hospital was sued in federal court.