I agree with jkelly, OkCupid
is more poly-friendly. Also, you can search on the term "poly" or "polyamorous" and find people who have mentioned it in their profile.
I second the honesty part. When I was on OKC I had a paragraph about me dating a poly woman, and while I'm sure it cut my responses by at least 90% the ten percent that remained were the interesting ones anyway.
As far as jealousy, anxiety, and angst go...yes. That's something both men and women experience when their partner is poly. Believe me, you ain't alone. I don't know any cure, but familiarity with the situation and especially with the guy involved as a secondary may bring those feelings to gradually subside.
I can tell from your writing that you're thoughtful, coherent, and rational. Those qualities are a great help, man! But as you yourself say, emotions come from somewhere else. You have to have feelings, though, or you're dead.
My poly (ex?) girlfriend had me meet her husband and we had a very pleasant time. One key was the sense of generosity and intelligence with which they both deal with poly. Also, we automatically refrained from touching or showing physical affection in each other's presence -- politeness, but also a way of respecting each other. That might work for you guys, especially since the gentleman seems to be, in fact, a gentleman.