It seems like a very divisive issue among Christians going back many generations? I think Christ and Paul were strong with their words about divorcing. But apparently what to do about abuse was not mentioned, other than instructions on not being abusive in the first place. The Word says not to associate with Christians who are abusers with their words or physically. I think if you are separated for long enough it is basically a divorce, including if you no longer talk or live with a spouse.
There are different responses in regards to affairs and abuse, whether or not you can divorce and remarry. I can't offer any clarity, but I believe the message was that if you treat your spouse right that divorce shouldn't need be considered. A true Christian wouldn't cheat on their spouse while married, so in my humble opinion I don't think you should be required to stay with someone when they break their Christian vows.
“As I walked out the door toward the gate that would lead to my freedom, I knew if I didn't leave my bitterness and hatred behind, I'd still be in prison.”
― Nelson Mandela