Would a narcissist ex-boyfriend talk about his ex to mutual friends in a way that makes it appear he is decent and moral when in reality he is trying to just take another dig at her?

OF COURSE! Mines is doing that now. They'd do anything to make themselves look like the saint. That is classic narcissist behavior. You have to be pretty careful in knowing who your friends are and who the narcissist has gotten to. I hate to say it but in order to figure out what the narcissist is up to, you have to think like a narcissist. Of course that makes you look bad, like you ARE a narcissist (you've probably picked up some narcissist behaviors being around one anyway) so BE CAREFUL. My narcissist called this game "Ex Caliber" after King Arthur's sword. He said people who were pure and of good intentions could slip past his defenses. Translation: You better make yourself look better than the narcissist and dodge the mud he's flinging if you want to keep your friends!