Here's a tough question for you:
If your spouse abuses you and/or your children, are you still bound by your marriage vows? Specifically:
(1) Must you still keep your spouse forever? Why or why not?
(2) Must you still forgo all others besides your spouse? Why or why not?
(3) When does a marriage end? When are the vows null and void? When one partner (i.e. the abusive spouse) first breaks the marriage vows, or marriage contract, by abusing the other partner and/or the kids, or does it end only when a court of law says it ends? Why?
And, to make this interesting, please keep in mind while answering the questions that life is seldom black and white. In other words, a manipulative, abusive partner might also be a good provider, for instance, just as a manipulated, abused spouse is unlikely to be lily white, either.
Abusive partnerships are by definition unhealthy. Whether the abuser is a good provider or not, that does not justify their abuse, nor is it sufficient justification for the victim to force themselves to remain married to their abuser.
If one's partner is abusive, and is unwilling to seriously and wholeheartedly confront that problem, enter psychotherapy and anger management therapy, take psychopharmaceutical therapy if indicated, kick any addictions that may contribute to the abusive behavior, and seek spiritual counseling and/or join a support group to help them turn themselves around and stop abusing, then one ought to leave one's abusive spouse as soon as possible. End of story.
However seriously one may take marriage vows, no vow should require one to sacrifice one's physical, mental, and emotional safety forever-- or even for very long at all. And I will never believe that choosing to remain married to one's abuser is somehow holier or more virtuous than having enough respect for oneself as a creation of God who deserves safety and well-being, and leaving the abuser.
To answer your specific questions:
1. One is bound by one's marriage vows until one has reason to get divorced. Upon divorce, one is no longer bound by those vows. But even before divorce, an abuse victim should separate themselves from the abuser, leave them, and wait in safety elsewhere for the divorce to come through.
2. One should not have sex with anyone but one's wedded spouse until divorced. Abuse absolutely warrants leaving one's abusive spouse and filing for the fastest divorce possible. But a high moral standard also warrants not taking the miserable failing of one's abusive spouse as an excuse to become an adulterer. Now, in cases where one has been married both in a religion, and civilly, my opinion is that whichever divorce is finalized first, religious or civil, is sufficient to consider the marriage ended and any ensuing sexual relations not to be adulterous.
3. Marriage ends when divorce occurs. Religious marriage ends when the religious divorce occurs; civil marriage ends when the civil divorce occurs. If one wanted one's relationship to be bound solely by one's own whims-- endable at a moment's notice, merely upon decision of either party-- then one should not get married. To get married is to widen the scope of the relationship from involving two parties, to involving three or more parties: the two spouses, the government, God (if it is a religious marriage), or other parties (in Jewish marriage, for example, that would be the Jewish People, one's community). One makes public commitments, formal and/or legal contractual promises. That means that the relationship can only be ended just as formally with a dissolution of that contract, and a public renunciation of the commitments of the two parties.
