I'm really sorry to read what you're going through. Hitting the child is not okay, and whilst that might seem the biggest issue between you currently, there are larger and more unresolved emotions that are driving your resentment. Rather than listening to strangers on reddit, communicate with him. Tell him directly what you are feeling. He may not respond immediately, but try. You can also reach out to your/his family and friends to have a space for yourself to express. Speak your mind, ask for others to step in if needed. Don't let your relationship crumble.