For your quantitative research and to ground your arguments in empirical evidence, these sites provide official data on crime, violence, and victims.
Bureau of Justice Statistics (BJS): The primary statistical agency of the U.S. Department of Justice. It collects, analyzes, and publishes data on crime, offenders, victims, and the justice system. The National Crime Victimization Survey (NCVS) and National Prisoner Statistics (NPS) are particularly useful.
FBI Uniform Crime Reporting (UCR) Program: Provides statistics on offenses reported to law enforcement agencies across the U.S. Look for data collected via the National Incident-Based Reporting System (NIBRS).
National Intimate Partner and Sexual Violence Survey (NISVS): Administered by the CDC, this survey provides comprehensive data on the prevalence of intimate partner violence, sexual violence, and stalking in the U.S.
National Network to End Domestic Violence (NNEDV): This organization provides data through its Domestic Violence Counts: A 24-Hour Census of Domestic Violence Services. This is a good source for statistics on shelter usage, hotline calls, and service needs.