Poly Amory is a very strong filter. By that, I mean if that is your primary filter for partners, you may be filtering out most other desirable combinations of traits.I'm not sure what they're telling me: that I'm being stubborn? They could also just be telling me that polyamory doesn't make them specifically happy, and that I should find people that value it.
This is NOT me trying to talk you out of it. This is me saying that you need to decide what is a deal breaker for you, and not compromise. By the same token, you need to be willing to compromise where you can.
By the way, to an older man, your ideas of how couples communicate, seem... naive. Again, not saying not possible, just unlikely.
You are the ivy league grad here. What are the odds of finding the unlikely subset of the rare subset, of the minority subset of the.... Ad nauseum.
Then, when you have found her, have you developed into the man she wants to keep?
Being the man who found and married his unicorn, I don't wish to dissuade you. My point is that you need to be flexible where you can in your search, and ensure that you can keep her when you find her, you may not get another chance.