You described my husband - soon to be ex. I really do not know, Fuzzybear. I spent the last month being enraged over his mistreatment of me, and unloading it all on him. I've exhausted that path. Then this morning after watching a long documentary on abusive narcissists (which is my husband), I found some amount of compassion for him. I thought, it must truly suck to have SO much insecurity to the point of needing to harm other people to keep them down. And with narcissism, their self worth is constantly in flux. So, I thought, wow, that must be really hard, and I felt a smidgen of compassion. Perhaps having compassion for someone else's major struggles (that cause them to react in SUCH hurtful ways) is a pathway to forgiveness. Then again, I also feel some things cannot be forgiven. Like, I do not and will not forgive his infidelity. But the compassion I felt today has enabled me to feel some amount of healing to occur. And maybe that's all that's really needed, above and beyond the act of forgiveness. Forgiveness to me is really more so about letting go of the anger, the anguish and the pain that someone caused you. I think of him as being a very small and weak person, and for that I can feel sorry for him.

Sorry, I am not really answering your question about how to forgive. But it's an answer nonetheless.