I feel for you, OP.
I'm going through a lot of the pitfalls of poly right now. It's become hugely stressful for me, and after a lot of discussion we've come to the conclusion that there needs to be a serious overhaul in Alex and Jenny's relationship so that the three of us can work it out. As for me, the only thing I could do to alleviate stress is get a primary relationship. My problem is that all the guys I meet say they're not into poly. The people in the poly community here are reluctant to get with me because Alex is bi, and most men around here (and some of the women, even) are very homophobic about it... a double standard that hurts Alex and makes things harder for me.
I'd like to think poly works, and in theory it does, but in practice, it's a whole different story altogether.