Ok, I don't understand what happened. You guys both let SMIL rile you up and push you farther apart....why didn't you both agree that she's overstepping and agree not to let her get to you? Wife probably felt threatened that even her family has turned against her, afraid that she'd taken a step towards a reunited family -then gotten smacked for not being willing to take 100 more right then, and it sounds like you guys engaged in a relationship convo right when you were both all worked up about SMIL's interference?
Come on, you're no rookie. Sometimes you have to put yourself in the other person's shoes and not let things escalate (and others should do the same for you). If it's done and you're fine with that, just keep it as a lesson for future relationships (including the one with your ex and D).
Sorry you had such a rough time - I HATE when other people start meddling and don't listen to me. Good job trying to get SMIL to stay out of it though - being honest about what you want and setting boundaries is a good thing, I think. And women love a man who will protect them. Good things to carry forward.
Faith is, at one and the same time, absolutely necessary and altogether impossible. --Stanislaw Lem