The first thing we have to establish is a boundary between fiction (The TA story) and real life.
In real life: My personal perspective, but backed up by having been married and countless conversations with married adults; you marry someone because you see a person you can have a partnership with, someone you love and respect and someone you want to build a life with, sometimes that involves bringing children into the world, sometimes not. But here's the deal even people who love each other fiercely aren't always on the same page, and there can never be a state of pure equality. And that's where compromise and sacrifice comes into the picture. It's a give and take relationship by nature. Spouse A wants to go dancing, Spouse B doesn't like dancing, but they compromise, they make a personal sacrifice because they know how much joy Spouse A gets from dancing. On the other side of that Spouse B wants to live next door to their parents, but Spouse B doesn't - so they compromise by living within a mile of Spouse B's parents. Spouse A isn't a morning person and doesn't want to get out of bed to make coffee, but what they adore more than anything is seeing the smile on Spouse B's face, when they feel heard and appreciated, because Spouse A made an effort to show their love. These may seem insignificant things on the surface but a marriage is full of these moments of sacrifice and compromise for the greater good, because each spouse wants the marriage to work, to last.
Regarding the Slave/Property comment: A marriage isn't built on permissions or obedience (unless each has agreed and consented to that type of lifestyle). It's built on mutual trust and respect as its foundation and love for one another that binds it. Each spouse has to trust the other will behave in a way that does not harm the marriage, or disrespect their partner. Entering into a marriage with the mindset that a spouse must seek permission on how to dress, or who their friends are, or what they should think; that isn't love - that's divisive, controlling and abusive behavior - it's the antithesis of what a marriage is meant to be.
As for your scenario, at heart I'm a serial monogamist. If I'm in a committed relationship they are the center of my world and I have to trust that I am the center of theirs. I would hope that they would have enough respect for me to have a serious discussion about their needs and why. And if I could meet their needs we could find a path forward (and for the record, being intimate with another would be a deal breaker for me), but if I couldn't meet those needs I would be honest with them and would seek to dissolve the union.
It's late and I'm tired, I'll follow up on the fictional side of your question later.