It sounds like she is truly, unfailingly monogamous. It also sounds like you have been extremely mature and open about your inclinations and desires (which are polyamorous).
So it sounds like the only place where you can exist romantically is back where you were, in a defacto monogamous relationship with you being open and honest about your polyamorous beliefs.
So, the real question is how long do you think you could be happy in a defacto monogamous relationship. Maybe you love her so much that you would actually be happy being a "polyamorous martyr" of sorts. Willing to be defacto monogamous for the love of a woman, but still being a polyamorous person and espousing a belief in polyamory. Or maybe you would grow bitter with that over time. Only you can really figure that out.
I think a lot of us can feel your pain. There are many people here who, to varying degrees, relate to being surrounded by poly intolerance. Maybe you feel so strongly about polyamory that you eventually want to live in Seattle or San Francisco or some other community where poly-friendly attitudes are easier to find.
Again, only you can tell you how strongly you feel in one direction or another.