I don't think he knows what his lines are because he's never been in a poly relationship before (he doesn't even identify as poly, which is a reason I always classified our relationship as a friendship).
Could let him worry about his own lines and you worry about YOUR lines:
- If you know this guy is not cut out for poly, why keep trying to poly with him?
- If you know you are happier in a primary-secondary model and you are NOT happy in a co-primary model, why are you in a co-primary model right now?
- If his insecure/speak from fear thing turns you off and makes you doubt he wants to BE with you -- why BE with him?
Could sit with those things and think about where your own lines lie and where you willingness to stay in this space is at.
If you strip your example down? It plays like this.
- I spend day with hinge.
- I ask him to spend night. He says no, he has plans with OSO that night but will drive me home. I am ok with it.
- On way home we pop in at potluck that is on the way.
So far so good. Then? All this other stuff? YOU do not need to know any of it. He is oversharing:
He later informed me that OSO was mad that she hadn't been invited to the potluck, because it's an event he's been bringing her to. She felt like it was a public event and she wasn't invited because I was there. He also told me that he would have picked her up on the way there but didn't want to ask because he thought it would upset me.
Backhanded oversharing all this does WHAT for you? Make you JOYOUS? Nope. You end up feeling guilty. He doesn't want to "upset you" and then he overshares and upsets you anyway. For what?
Well, you could choose to change your behavior when he does that
"No. Do not tell me. If you have things to tell her, TELL HER. Do not put me in the middle. If she has problems with me, she can tell me direct. You don't have to be put in the middle. If there are things we need to cover in trio, let's talk in trio. No playing he-said, she-said. Let's go for all in a room, everyone airs it out in the open. I am willing to attend trio talks. "
Lather, rinse, repeat.
Now I feel guilty for having put them through that.
You did not put him through anything. He could choose to say "NO" to your requests. Poor management on his part does not make it a crisis on YOUR part.
That's where you are over-responsible. Own your own emotional baggage. Do not take on other people's. Encourage him to own his own baggage. Not sit around dumping bags at your doorstep.
If you are happier as a secondary in a primary-secondary model and he wants a co-primary model but isn't making it work, you could talk about going with the other model. If it works out better, yay.
If it is still an on going drama thing -- you could evaluate if it is worth the bother any more.
I mean that kindly -- because YOU are the one ultimately responsible for your own health and well-being and so far you don't sound happy and thriving here.
Take charge of your own life! You can do it!