"We are emotional animals, no amount of reason can overcome that fact."

Yes, it (reason) can and does.

If human beings were simply emotional animals, acting on as well as unable to overcome "the range (and sometime rage) of the moment" the species would have become extinct tens of thousands of years ago.

That's the purest nonsense. In fact, there are thousands if not millions of people in various types of stable polyamorous relationships.

Jealousy may be human nature but it is totally amenable to being brought under conscious control, just like any other emotion.

The more I think about it, the more it seems clear actually that any type of agreed-upon monogamy is nothing but an attempt to coercively control someone else's emotions and life.

Interestingly, this is fully explored in Atlas with Hank's relationship with Lillian. Note that Dagny is never married or engaged or explicitly monogamous with anybody. Not a coincidence in a book where nothing is a coincidence.

Indeed, Rand herself was famously and openly and honestly polyamorous as well! Another idea she was one of the first to come up with and implement.

Which is not to say there isn't a lot to be said in favor of a long, possibly lifelong partnership resembling a traditional marriage. But even that would work much better without sexual monogamy. That's a whole other topic I can't get into right now. And anyway, the state, through various forms of social engineering, and also just as a side-effect of its parasitism, has done a pretty thorough job of destroying any possibility of that really happening in any meaningful way or numbers, it seems in all western countries.

Oh and Hank didn't give up on his marriage, he was rescued from it. He is grateful to Dagny for opening his eyes and happy for the time they had together and would absolutely never try to stand in her way if she decided that Galt is who she wanted to be with now.

A great movie dramatization of that idea that I always liked is in Indecent Proposal - in how Redford's character (named John Gage - hmmm!) handles his affair with Demi Moore's character at the end. (And actually also in how Harrelson's character eventually deals with his jealousy). I always thought that movie perfectly illustrated Rand's ideas on romantic love being based on objective values.

well the characters are meant to represent ideals not day in the life. How many novels can you read where we are supposed to accept a hero who is wracked by jealousy, demons, bad decisions in the past-you're supposed to root for him to overcome his demons and maybe he does at the end-maybe not. ugh