Originally Posted by Legion
Okay, my perception from reading this thread is that your husband likes/loves you and wants to continue a relationship with you, but he also has some nagging thing in the back of his head that he wants kids and that he's not going to be able to have them with you. Maybe that's his only reason for wanting multiple partners, or maybe he has other motivations, but I perceive that this is a very real and major motivation for him. So naturally if you make it a rule that he can't do what he specifically is wanting to be "poly" for, you are going to butt heads.
But he ALSO seems very self-focused like nobody else's needs or feelings matter. I can STRONGLY (very strongly) sympathize with the desire to become a parent, but that does not excuse you loosing your humanity and treating people badly. When your whole attitude becomes "WE are going to become polyamous, but all of the decisions about how we're going to be polyamorous are going to come from ME," then you end up with worthless polyamory.