Because someone who is truly in love & proud to be with you will speak well of you to their mates. They won’t denigrate you when yo ur e not around & speak poorly of you behind your back. They will want you around & wont be afraid to show it.
As for everything else, therapy would be wise to work through your deep rooted self esteem issues. You say cheating is your worst nightmare, but we’re willing to drop what this means to you & forgive him in order to keep him. So you were willing to drop all your values in order to be with someone - that means you have no self esteem. Because you don’t matter as much as the other person does - very unhealthy.
You’re exactly right - the nicer your are, the less people tend to respect you. Think about it - if you were not keen on a guy romantically, but he wanted to date you so kept on being “nice” - why would that make you like them more? You can’t behave your way into love, it doesn’t work like that.
Also you say you wanted him to realise his lad life isn’t as good as what you had - but with that mindset you need to be “the bitch” - tell him to get fucked, lose your number, get lost.
He doesn’t feel the loss of You, you’re still there in the background & he knows he can pick you up again anytime he likes....
You haven’t lost everyone you love. You have to your children. These victim like dramatic statements are really counterproductive to your healing. We all face loss of love. I cannot speak for your childhood & it sounds like therapy may be a good option for you, to unpack all of this.