"If my SMV is 5 and my girlfriend's SMV is 7, it is likely that she will cheat on me with an SMV8 guy in the next 12 weeks" This statement tries to simplify a vast number of different circumstances that cause cheating/breaking up. If you and a girl are dating, and there's someone out there she likes a lot more than you, and the difference is so huge that she'd rather throw away all the time and energy (if there was any) invested in your relationship... Yeah, it could happen, but what I've talked about is just one case. The whole SMV thing is an oversimplification, if you pick someone who doesn't have everything that you ever wanted, and you're not happy with your current relationship, people might move on. Additionally, if the girl or guy believes that creating a new relationship with someone a little better or a little different will make a world of difference. There are plenty of people who are wise enough to realize this isn't the case, at least if both partners were enough of what they wanted.

And I am still, a freaking 18 months after breaking up and 6 months after last contact, not 100% over my ex. sigh I was 'triggered' a few days ago by thinking I saw her in the supermarket, carrying a pram…I feared the worst, yet was happy. Bittersweet. I think this is less about your ex, and more about all the change you have to make until you can have a happy relationship. The experience appears to be more of a tool, a set of experiences you didn't quite understand that you test your understanding against. Alternatively you could try for new experiences, though I sympathize if you feel that would be too painful--espcecially if they go wrong.

You might like that book I linked in the other comments, at the very least it might provide an alternative to those screaming matches with your father.