So you hard swing, and he's more poly because he wants emotional relationship and not just sex in there.
I'm very fearful that someone will try to take him from me, or less so that he will grow to love someone more than me.
Isn't that kinda backwards on the first bit? How can anyone TAKE him from you? He's not a cookie. Isn't it enough to be a good partner he doesn't want to leave and enjoys coming home to and being with?
I used to have a partner that drove me so crazy. I loved him so, I was fully present, loving all my hardest. I wasn't even DATING anyone else at the time but he was SO stressy with the jealousy and anxiety about "worrying someone would take me away?" It shattered the rship. It was more the nonstop anxiety yammer, and the unwillingness to process what this was coming from, and worse -- paying THAT "what if?" thing so much attention but not paying ME any attention. I could understand the jealous had there been another partner. But there wasn't. He was "what if" clouding tempest teapotting and it made him not fun to be with.
I started thinking "God, this THING between us. I am not even DATING anyone else. We are essentially closed right now. And he's still going on and on. I make love deposits, and I never get any deposits back,. It's all drain here, he's not even in this rship -- he's guarding me looking out all the time. I feel like a thing, a trophy. Not person. It is tiresome, and I think I prefer to be ALONE and not dating anyone than WITH HIM and not dating one. It's THAT tiresome. So I broke up.
Food for thought.
On the second part grow to love someone more than you? When I think about who I love most, my kid and my spouse... I don't see my loving my kid taking anything from loving my spouse. They are different people, and I enjoy them for different reasons.
We are closed now, but when we were open? I loved my loves -- I didn't love any of them MORE than the others. I loved each for a different reason - one fed my mind and heart, one fed my body and heart.
That's cool that you learned this though:
Most recently, we closed the relationship as an experiment. It yielded a lot of positive things and brought us closer in many respects, but we both knew it was not a lasting solution.
Why is this not a lasting solution like seasonal answer? In spring we are thus. In summer we closed for a season to strengthen. In fall we are thus. In winter we are thus. In your hard swing style, a "summer break" is nothing to your partners.
For his poly people, a "summer break" might require more negotiate-y depending on what stages his rships are at. But seriously? Can't give the primary a summer vacation? When he's present the other 9 mos a year?
Or maybe some other pattern. 3 mos open, 1 closed maybe.
I'd explore what you learned about that period of "closed" if it fed whatever it was that needed feeding so well
you were able to go all the way open afterward as the next stage of your relationship process.
I think you are on the road to a solution for yourselves... just gotta hit the sweet spot pattern maybe? And learn more what IS getting fed with that?
Just some thoughts.