I am glad you came here, too, Vanilla, since it is good to get both of your takes from the situation.
I wonder, do either of you see the ways in which both of you are acting passive-agressive? And the co-dependence you both are contributing to? Does it feel loving to you? What about the constant drama, is that what you really want in life?
It feels to me that both of you have quite an unconstructive approach to any relationship problem. It's always somebody's fault. Sometimes there's a disproportionate amount of blame directed towards oneself. Sometimes towards the partner. Sometimes the fault is seen to be fully in the metamour. It may or may not be deserved, mind you. But it's not the most relevant question. Really, it seems to me that you, together, create quite a co-dependent relationship dynamic. Even without other partners and NRE and stuffs to complicate things, I feel you'd need some work on communication, confidence, self-love, and boundaries.
I actually agree with BrigidsDaughter, while I normally wouldn't say this, I do think it might be best to close things up. To build a really strong, stable foundation for the two of you. I mean, it seems to me that that is the first priority for the two of you? I do thing poly is adding a lot of drama, and it looks like you are moving to more and more unstable ground all the time.
Psychologist, the best idea in a long time.
Moving out, maybe not the worst idea. I do agree with Vanilla that it is sort of running away from the issues. Similarly is the suggestion of becoming (possibly temporarily) monogamous. However, I feel that somehow you need to get to a more calm and stable place, whether together or separately, if you don't wish things to continue as they have been.