I don't feel bad that I've said that. Maybe it's not my place but whatever. I do need to do a better job of shutting the F up about her for my own sake.
It's your story too.
Like Mike, I practice mindfulness. Sometimes I think, "Oh yeah, get back in your own lane, Florence."
She moved on, as people do after breakups. Maybe what you're seeing now is validation that she lacks boundaries and needs to be with someone at any costs -- anyone. How does it affect the kids? The kids see that mom's priorities are on herself and in spite of whatever attention they need. Either way, it was what it was. You loved someone who was broken, and it hurt when it was over. As these things do. Let go of any fantasies that this new relationship is good. Until she gets right with god, herself, and her kids, whoever she's beholden to in this world, she will remain a locus of pain and chaos.
A suggestion? Stop worrying about whether your grief is manly enough. It's okay to feel uncomfortable and sad and worried and lonely sometimes. I used to swing between, "What is so wrong with me that AH couldn't love me?" and later "What is so wrong with me that I loved someone so broken?" It was a bad line of thinking, but at least the focus was on me, and what I can do about me.