Congratulations on the good news.
How soon after the news did the open marriage talks start ....on the ride home ?
We're you too clingy when they thought she might die or were you a rock ...or is that what she was looking for in a rock.....a clingy rock?
It sounds like she has a plan with one particular guy in mind and you keep mucking it up ( in her mind you keep mucking it up )
I'd say it sounds very unreasonable to not even listen to your ideas.
I don't know what was on your list of fears and possible negative outcomes but I know this. Someone who says their not sure they want to be married anymore and doesn't know why is being naive by making assurances that x, y and z aren't possible. Most or things are possible it just some risk factors are cut down. And feeling are ever changing and can't be predicted. Yours included.
Is your wife sure now that she wants to be married and why? Has she sorted that out by herself or with the add of a professional?