The following story illustrates the complexity of abuse. If you want to used the heter of rodef to call the police because the abuser is endangering the victims life - you also need to understand that it is an issue of pikuach nefesh in being labeled as a victim of abuse and having your family labeled as containing an abuse victim. That stigma is also pikuach nefesh.
Brisker Rav (Rav Zilberstein Assia Nissan 5747): There was a case of a sick person who requested that the doctor allow him to fast on Yom Kippur. This was because his condition had significantly improved and his life was no longer in danger. The Brisker Rav told the doctor that pikuach nefesh doesn’t mean that right now there is a danger that might cause death. Rather even if fasting influences him so that when he has a recurrence of the illness - that he will die before his time – that is also considered pikuach nefesh. Therefore the sick person is obligated to eat rather than fast on Yom Kippur. The doctor replied that the aggravation that is caused to the sick person by his awareness that he is categorized as being in a fragile condition is liable to endanger his life. The Brisker Rav accepted the doctor’s words and replied, “If so we have to think very carefully how to act.”