I think at times like these, you have to focus on what you can control, which is your own self, and your love for your daughter. No matter what happens, those two things will be central to your life. Focus on being okay within yourself, about yourself. Sometimes when contemplating the insanity of the wh's behaviour, it seems like we need them to be okay within ourselves. Sadly we have learned that the only person we can completely trust is ourselves. You can do this by finding the things that give you pleasure - reading, friends, movies, tv, spa, bubble bath, whatever that may be, and pursuing that, really dwelling in the space of those positive things for you. Think about your own value, rather than focusing on his valuing of you or lack thereof. Surround yourself with people who value you and notice the difference. If you find your h is not one of those people, then that is a choice you can make to not be around him if you decide you need to do that. As for hitting your h - think of the context of the situation. Is this out of character for you? If it is, it is likely something for which you feel great remorse, and which therefore will likely never happen again. Perhaps you felt you had no other way to get his attention, wrong as it is. If he is not acknowledging you, and you are going to such lengths to hurt yourself - perhaps so he can notice - then possibly he is committing emotional abuse through his lies and deceit. I know it's so hard, so I am feeling for you.
Did he tell you he pursued the relationship and that it was ok because he didn't love you? That sounds like gaslighting logic. He's trying to baffle you with bs. He made a commitment, so it's never okay to pursue such a relationship that violates the vows of marriage - even if you don't feel "in love" anymore. He always had a choice - of being honest with his feelings and the problems in the marriage, turning toward his partner vs. lying and causing you great pain through his selfishness and betrayal. I hope that helps in some way. Hang in there.
Married 10 years, together for 15
Me: BS Him: chronic boundary issues, EA for 2 years, DD Spring 2013, Separated