Dear Troubled,
It is never easy being caught in the middle. Although you had not asked any specific question, I suspect that this comes from how painful it is to even consider what options your family has.
Given your current circumstance, it may be better if your daughter moves out. This will help alleviate the current condition of your wife. It may even improve the current family relationship. This suggestion challenges the notion that staying together is always essential for a good relationship. Having clear boundaries may help improve or at least minimise conflicts.
However, to ensure that this suggestion is not misconstrued, here are some suggestions as to its delivery. Firstly, present the rationale as a way of preserving family harmony, not as a rejection of a family member or ridding the family of a troublemaker. Secondly, involve your daughter in the process by talking about a timeframe and giving her a choice of where to live. You might even suggest a place that is not too far away so that it may be convenient to visit each other. Thirdly, if possible and if needed, offer her any financial help to make such a move possible. Finally, do emphasise the desire to maintain family ties. This may be in the form of regular family meals.
As you take such a move, be prepared for some sadness on your part to see your daughter leaving the home. Such sadness is part of the process of letting go and letting her grow as a person. It will also give your wife and you some needed breathing space to deepen your relationship.