Hey, whatever it takes to get you to post
Seriously, I've always viewed open-relationships as a type of swinging. As I posted elsewhere that is basically what I had with my ex-husband when we first got into all this. We swang (is that even a word?) together as well, but I would say most often it was each of us doing our own thing.
You are right it does put you in a much harder position than it does her for the very reasons you listed, but it doesn't make things impossible. Actually, the fact that you are doing the open relationship thing makes it easier than if you were just "swinging seperately" or actually cheating. In your situation you aren't really looking to get with couples, you are just looking for whatever. You aren't trying to make something happen (like most single/married guys we encounter in swinging). So just continue with what you have been doing and see what happens, and know that if someting does come along you can be open to it and let it happen.