Really good piece asking really good questions. We went through something not entirely dissimilar a couple of years ago when I got what felt like a call to open up our marriage to another man. We were at a very happy and sexually exploring stage so it wasn’t boredom or lack in my primary relationship. He readily agreed as long as we could explore with a woman also and we embarked on a lot of discussion and soul searching, which was very healthy for us both, as well as some fun sexual assignations. When we finally found the guy I’d been looking for (it turned out it was a particular guy and not just any old guy) it was someone I was instantly deeply connected to and a part of my spiritual growth trajectory.
The fact that we’d explicitly planned for this to be sexual and not emotional really rocked the boat for a while, but since this wasn’t about something being wrong in our relationship and it felt vital to my own path to keep pursuing it, I finally had to take a stand: I told him to do the healing work he needed to do in order to accept this fully (he did accept it some of the time) or get out of the way because this was no dalliance or whim — this my life and there was no turning back. It was a bit dicey there for a while, but when he did finally clean up his old wounds, the insecurities around all of this melted away.
Now he is perfectly fine with me having another life partner and they consider each other as members of extended family. Our relationship has continued to grow and blossom and in fact, I just wrote yesterday about how all of this has helped me to really reclaim myself in a variety of ways. Yes, we create boundaries and parameters that we’ve negotiated together, but he doesn’t own me or my body and even though he never would have consciously indicated that he did, there were possessive elements in there based in societal programming about what marriage means that, once dismantled, improved both of our lives tremendously.
This is not meant to advise you on your situation; merely to say that I have some understanding of what you are going through and I hope that you are able to work it out in some satisfactory way.