My mother told me a long time ago...."You can't have a conman without a person willing to be conned". It took me years to fully grasp that in regards to relationships or marriage and the roles we play when not being truly honest with ourselves or another.
In many, if not most relationships, we all start off by offering up only our 'best selves'. Both sexes are guilty of this. And when we seek out a relationship, most times, we ARE asking "what will I RECEIVE out of this relationship or marriage". Rarely do both people enter in only saying "what can I GIVE completely". (Which would actually be the optimum mindset, thereby, both people actually benefit from the mutual selflessness) Our 'best selves' are merely a sales technique to close a deal in order to receive. In essence..... each of us can potentially be "conman and conned" at the same time depending on actual intent. Most people's intent seem innocent enough. Nothing wrong with WANTING love. But sometimes we tend to jump into something out of need more than to give.
As I read this whole thread, while not wanting to make total judgment call, I can't help but sense that there were two people who played into this scenario with each other. If the situation is truly violent, then even Jesus would not tolerate abuse simply to prove a point of martyrdom. Jesus acknowledged the woman at the well, knowing she had been married five times..... he extended grace.
Sometimes people do not leave what they know to be a bad situation, one they might have even caused themselves by not admitting the "conman/conned" persona inside, because they simply have no other place to go at the time..... some stay from guilt of their own mistake, refusing to admit they kneejerked themselves into 'love'.
I recommend a book called "Boundaries" by Cloud and Townsend to any person who is still stuck in trying to establish what would be acceptable levels of behavior from somebody else, and then applying the concepts, before making the ultimate decision. Most times, boundaries are crossed because we have failed to establish them. And once they are crossed, then there should be no TALKING about it anymore....... only action..... silent, and swift.
Prayers for this situation.... May God Bless the two of you...