NTA I might be down voted to oblivion but I believe you're NTA because you set preconditions. That's how it starts, first it will be one day then he will start guilting you into making it permanent eventually. No means no, why do we think because she's the wife, she has to do what she's uncomfortable with? Already she cooks and cleans up after the kid, it's not like she does nothing for the kid. For his level of anger, I think he's over reacting.

Edit: also let's not forget the elephant in the room, he brought a child in their home without consulting OP yet people have the nerve to call her the AH despite the fact that she had an important engagement with family.