I'm sorry you struggle. I mean this kindly, ok?
You don't sound like you are behaving poorly at either of them. Him and her can break up on their own -- it's not like YOU are making them break up.
At the same time, you and him can break up on your own. It's not like you have to put up with crap behavior from him if he behaves poorly at you.
SO WHAT if he has another partner? That gives him a pass to behave in ways you don't like in YOUR life?
Set and enforce your personal boundaries for what you will and will not put up with in your relationships.
Your personal boundaries are for YOU to set and enforce/obey. They help you keep free of shenanigans.
Nobody has to like them but you. So I think it's fine for you to have these personal boundaries:
- "I do not want to share sex toys with other people. If he wants to use the same toy with both of us, I say "No, thanks. I prefer separate toys. She can buy the same model, but not use the same actual toy." If he pushes on this more than X times? He won't change his behavior? I drop him because he won't respect my limit."
- "I don't want to hear TMI details about him and his other partner. I want to hear basics like sex labs, condoms, safer sex practices are being used so I can give informed consent. I say "Stop, I'm not up for this. Please respect my limit" if he tries to overshare TMI details. If he pushes on this more than X times? He won't change his behavior? I drop him because he won't respect my limit."
- "I prefer a separate V. I prefer a hinge not leak their problems on that side of the V on to me on this side of the V. Reasonable things like calendar and ____ are ok. Oversharing about ____ or trying to make me the free therapist for their couple problems are not ok. If he pushes on this more than X times? He won't change his behavior? I drop him because he won't respect my limit."
Practicing a primary-secondary model doesn't mean good manners flies out the window.
You are still a person. You still have your own preferences and your own boundaries.
Your life is YOUR LIFE. (Your life) is NOT (their sex therapy tool)
just because they have mismatched libido. That's on them to solve over there
on that side of the V. Nothing to do with you. It might be the reason they opened up the relationship.
But over here in YOUR life? He's just some poly dude you started dating. Poly dudes sometimes come totally single, or sometimes come with established partners. So what? It's poly.
HE does have to make the cut for YOUR personal standards as a decent poly partner. So... does he make the cut or what? If he's a sloppy hinge in some ways, Ask him to shape it up. If he's behaving like a poor partner? Ask him to shape it up.
Does he HAVE to change anything? No. He is free to keep behaving as he does.
Do you HAVE to stick around? No. You are free to choose to be elsewhere. You can drop him because he doesn't make the cut for what you are seeking in a poly partner.
Keep your life simpler. Focus on you, your life, your side of the V and whether or not this guy is actually compatible.