I don't want to leave, mostly because of the kids, but partly because I know it will completely crush and destroy her.
You need her to go to counseling. If leaving her will crush and destroy her, that is what she will need to hear will happen if she doesn't go.
Choose a counselor very carefully. Find one that is trained to deal with infidelity. We found ours via a recommendation from a group that deals with sex / porn addictions and infidelity (they were too far away but knew other counselors). They will hold her responsible for her immature and selfish choices.
Without knowing more--she sounds like she holds you responsible for turning the OM away from her. It did end her round of fun.
She still is exhibiting serious disrespect for you. Ending the affair can't be the only condition for letting her back; she also has to recommit to the marriage and hold up her end of making it work.
But I hear you on the love thing. Cheaters, I think, just assume that the loyal spouse will always be there waiting for them like a puppy dog. There is only so much selfishness, however, that a good-hearted loyal spouse can take. And if you're done, it's because she never stopped being self-centered, even though the affair was over.