"You will drive yourself crazy wondering what you said wrong or how you said it. "
But in the OP's case, she KNOWS, JoJo. They had an argument and OP told her ED she "doesn't like' and enumerated things she feels ED has done wrong in her past (and one thing in the present). This was directly related to ED's feeling unloved. It's not a mystery. IMO, your post gave generic advice that might fit many situations but not this one.
As for your relationship w/ your DD, I'm sorry it seems to be checkered. And yes, it may be helpful for you to be more assertive. But while assertive may be telling an AC, 'I didn't like it when you did XYZ," it's NOT saying, 'I don't like you" (even if you give reasons afterward). In fact, IMO, assertive doesn't mean criticizing your (general parent's) AC's behavior towards others (except, perhaps, in extreme circumstances), it's more about standing up for oneself.
Karen, I'm sorry, but telling SIL all about ED's past would be vengeful at best (no, there is no reason 'he's gotta know" and at worst, would destroy any hope the OP has of reconciling w/ ED. HH's response to this idea was spot on! Alsbrights please don't do this!