Maybe its my training as a lawyer but I don't see what you prescribe as implicit in the marriage vow.
I think as a practical matter, one spouse saying 'Get lost' is all it takes (and that does not necessaily have anything to do with the As you mention). How can a person be expected to stay married to someone who doesn't want to be with them, and at worse, wants to be with someone else?
In my case, it was not implicit; it was explicit ("Til death.") Besides, Catholics have classes to take beforehand which are supposed to explain what the vows are about in the context of married love. Our classes weren't much, in my opinion, but at least they conveyed a couple of key concepts like "exclusive," "faithful," "open to life," and "permanent."
You wrote: "I think as a practical matter, one spouse saying 'Get lost' is all it takes (and that does not necessaily have anything to do with the As you mention). How can a person be expected to stay married to someone who doesn't want to be with them, and at worse, wants to be with someone else?"
I would not live with such a person. However, even if separated, I would still in reality be married to him. That is to say, the bond created by the vow would still be there; I would not be free to marry anyone else. I would have to hope and pray for his repentance, and the restoration of our marriage.
That's what "vow" means. That's what my mother and father meant, when they married each other. I just checked it out with my husband a half an hour ago: that's what he meant, too.
Whew! :o)