OP the most important thing to screen for in a woman is character. Character is independent of looks, and the more beautiful a woman is, the rarer character becomes. The reason for that is the fact that beautiful women have more opportunity thrown at them than you can possibly imagine. There is so much temptation because every man wants a beautiful young woman. It becomes harder to exhibit character when it is so easy to use men and behave in a transactional way to get what you want without regard for the other human being in the interaction.
Beautiful women who have character get scooped up and locked down by men who can obtain them, so as time passes (as women age) fewer exist in the dating landscape.
Character in a woman is what combats emotional reactivity and loyalty (the two things
@Clockwerk50 bolded in his response), although I am
using different verbiage, the concepts are the same.
Women with no character are aptly described in the song "Loyal" by Chris Brown, and you are never going to turn a Ho into a housewife.....be advised.
Food for thought.
But. Girls who do have character know what they have to offer and know what they are looking for. They can be tough to manage for a man without solid leadership skills as a number of the guys have mentioned. So they require a different, more evolved skillset than less refined women.
So you are looking for character. If your exgf had character she would not behave trying to get into VIP areas for free drinks at a club while she's with you. She wouldn't act that way if she was yours but not with you right then either. She wouldn't have tolerated off/on, and her mother wouldn't be egging on attention seeking behavior.
If nobody in her close circle (family/lifelong family friends) has modeled a successful relationship, who will she emulate? The dysfunction that is familiar to her. The broken ness. People gravitate to what they know, and it takes great effort to overcome that kind of relationship template inertia. You have better models in your family. Pay attention to them.
I cannot however wholly discount those from broken home backgrounds. My parents were divorced when I was 16, but they were both classy about it & ended up amicable after the initial emotional pain subsided. My first husband and I also divorced amicably, and we were very forthright with our kids about why it happened and what could have been done differently. And that was an ongoing open conversation over the years.
My parents were the only divorced couple in my whole family. So I did have solid examples outside my parents, and I had many friends from solid intact families.
Sometimes you do learn what you don't want to become by living through it. But that requires a great deal of self awareness and maturity, and character, and that character has to be rooted in a value system from somewhere that is deeply internalized.
Pull up the old thread How to Spot a Unicorn in the search function. There's some silliness in the thread, but you might find it useful about what to look for, and my story is also there, so you can be the judge of my experience & credibility if that interests you at all.
You are getting some great advice from some of the best contributors on the forum in your thread (and I'm not talking about myself). There are married men, divorced men, fathers, men who are very smart, successful in life and successful with women giving you advice here.
You will heal, you will become an improved version of yourself, and you'll gain perspective in time. We are rooting for you.
Cheers.