Aw -- I'm sorry you are feeling misunderstood. I wasn't judging you at all -- though I'm sorry you struggle with parents not understanding your wiring.
Me? I was trying to get a sense of what sort of background is going on here. That's all. So... it sounds to me like he's monoamorous for himself but poly-friendly? And you are polyamorous then? How you are "wired" inside?
How about reading resources together then just to build some common lingo and help you in your talks first? Then when you say something or he says something -- you both MEAN it in the same way and USE the word in the same way so your communication is on the same page.
I'd suggest these as first 3 articles you could read together:
Then branch out and you could explore more things to read:
Could that be useful?