This, right here, was the broken agreement. Everything after that is just adding to the mess. Your feelings are valid, and, from what you have written, justified as well. He's broken agreements with you, more than once.days later he informed me that she didn't even know about me yet.
I do agree that primary, in your instance, is across the board and you are a nesting partnership and
The pet name thing would be a big thing for me, too. I only sub to Puck, we don't switch, but I'd be highly unimpressed if he tolerated anyone else calling him Puck (if they knew I did) since that's the name I have for him. And actually worse for you since Professa/or are your titles for him in D/s and and they aren't generic and like Sir would be.
It's not cool that he let her use the same mode of address, they could, maybe should, have sought another title.
Also, as you describe it, primary is indeed across the board. Your relationship is just that, a full relationship, not just a kink contract, and you are nesting partners, too, not just roommates. You do deserve better treatment than his current limerance with this new woman is making him capable of. Call him out in it. He's screwing up and you have the right, as a poly partner in whatever form, to let him know his hinge skills are lacking.
Edit: I was writing as you posted and didn't see until after I hit publish that you have said your relationship is not necessarily labelled/classified. His infatuation with this new woman is clearly the issue, he's so enamored that he's forgetting his responsibilities to your dynamic.