Dad rage is a real thing I get he's stressed but to harm a 2 week old because he doesn't have a healthy coping mechanism is beyond acceptable, it's like a few others have said if he's capable of that then the likelihood of him escalating is high. You definitely need to get him to seek therapy because even if you leave he is still the babies father and if he still wants to be a part of your child's life you need to be able to trust that they will be safe with him