Think of a time frame for how long you will stay in the relationship with no improvements. Not just how long you can stand it, but how long is fair and reasonable to everyone including yourself. Inform your companions, and mark your exit date on the calendar. If things have improved by then, then stay with them for awhile longer, otherwise have mercy on yourself and let the toxic situation go.
That's my advice anyway.
Love means never having to say, "Put down that meat cleaver!"