I voted #3 mainly because it had abuse in it. I don't think abuse should be tolerated.
The other two would depend on the circumstance. For example if someone's illness made them unnaturally abusive.
The story of Sandra Day O'Connor is an amazing one. Would I be able to do it? Depends on where in the marriage we were at. If we were only a year into marriage and she completely deteriorated, probably not. But if it was towards out 60s / 70s and we have an entire history of raising a family together and we are almost a one person, then I would stay. Long memories of her and our relationship as well as deep empathy I would feel for this amazing person would not allow me to do otherwise.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~