Separating from one's husband who is involved in zina

If a husband is continuously involved in zina and is not even guilty of it, does the wife have the right to get separated? If yes, can she file a divorce instead of khula? Is such a right given to her in her nikaah agreement? What are the regulations in relation to khula and divorce? Can she give divorce? Does she have the right in her nikaah documentation according to sunnah? He will try to humiliate her to protect his image and even kill her if he comes to know that she knows he is a zaani. He will make it as painful for her as possible because thats the kind of person he is.