Hey there. I just wanted to say that I really feel for you, and to offer some thoughts.
It seems like you are in a tremendously difficult situation. Living with a metamour seems to always take a lot of careful negotiation and adjustment, but to also have her be your ex? Yikes. In general, no one wants to have to be around their ex more than necessary right after a break up, it takes time to heal. She is also very young (I know that I was way immature at 21), and it seems like she has a ways to go on her communication skills, and on understanding what she wants and what she can give.
Taken altogether, it seems really unfair to you to expect things to continue as is. You guys moved Chipmunk in as a way to get her away from her controlling Mom, which was kind of you, but based on the amount of time you were dating, it was probably premature, and now, based on all the factors above, it no longer seems like the right or good thing. Another factor is that it seems like she and Airyn are fighting a lot -- I would take this as another sign that more space would be better.
You mention Airyn not wanting her to feel like less than an equal partner, but how can a girlfriend of less than a year be "equal" to a wife and co-parent of many years? He and you have an OPP but, at least based on her pursuing J, there isn't one with her -- is that "equal"? Equality just doesn't seem like a reasonable expectation here. Now, of course you want to be fair to all involved here. But, as Franklin Veaux points out in this great essay --http://www.morethantwo.com/polyfairness.html -- symmetry is not the same thing as fairness.
Anyways, I don't wish to criticize you guys for making mistakes -- lord knows I have, in my day -- just to point out what I'm seeing.
Good luck with everything!!! I am sure that you will find a woman who loves and wants you for you in time.
The major players. Me, 30ish bi female. Gia, girlfriend of 4+ years. Clay, boyfriend/dom. Davis, ex/friend/"it's complicated." Eddie, roommate & fwb.
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy and Nikki, Clay's partners. Liam, Eddie's husband.