Nice article, thanks for sharing Marianna! It seems obvious to me in your situation that there was definitely a primary partner, all the more so because of the children and resulting custody issues (and issues whereby you'd have no legal rights in our judicial system).
I find in polyamory it's easy to say terms and not mean them at all. When my wife wanted us to try poly, she really just wanted the stability of the shared family home while shopping around for her next monogamous partner (whom she now describes in her Tinder bio as "looking for her soulmate").
Your point about needing to define clear boundaries and continually revise them is spot-on.
In my case, we had discussed boundaries, and she ignored clear boundaries about cohabitation we had never discussed, keeping those behind my back. So the "ethical" in "ethical non-monogamy" went out the window.
I think the closest you could ever find to "non-hierarchical polyamory" would be in a bisexual partner with committed relationships of different sexes, or else in a true "throuple" (especially all the same-sex, like 3 husbands).