My advice is to be a loving and supportive Father (which it sounds like you are), and pray that your Daughter has enough self worth to avoid those types of men. Ideally you could show her and she'd just get it......but some seem to seek out toxic relationships. If she is cooling off with the current guy b/c he's self-centered, she could be on the right path, and really learned from the past.
I have two teenage boys so no father/daughter experience to draw from but I try to imagine how protective I'd feel over a daughter. I commend you for not giving the Ex a lead enema..
I'll share a quick story. I have a friend, ex pro football player (back when they played for the love of the game and love of hitting), tough as nails and never minced words. He has 3 daughters, a set of twins and another, all are drop dead gorgeous in their late 20s/early 30s now. He had a routine that he perfected whenever one of his girls brought over a date. He had a mason jar with two large "Rocky Mountain Oysters" floating in water, and would place it on the middle of the kitchen island. The new young man never failed to ask what it was in the jar. My friend would respond that the jar contained his trophies from the last guy that tried to do anything to his daughter that she didn't agree with. And he would deliver the message in a way that left no doubt.
I swear to you that's a true story. Good luck buddy....it sounds like you're already doing the right things.