There are many who choose to stay because of their children. I wish they would ask themselves if this is what they want their children to think that love is about... Children know when their parents are unhappy. Children often find themselves in the same situation in the future. Finally, many people tell themselves they stay together for the children but in reality they are too afraid to make a change.
A lot. If it's a dangerous marriage it's not best for anyone, sometimes lack of a parent is better than a bad parent or seeing a parent in a bad situation. Seek counseling and look at all aspects of the marriage, there is no right or wrong thing in these situations, people are hurt either way. Pray about it.