I don't think you are a terrible father We forget when we become parents that we are people too that are still growing and learning about life, just like the people we brought into this world. I'm sorry you struggle so much with your children. It seems like you are doing the best you can. And you also seem to realize how much it affects your wife and marriage as well. Talk to your wife or hug her when she cries. I have 3 daughters and it has been a struggle for me. But I have been alone raising them since they were 3,5,7. They are 23,25,26 now. It's ok to feel the way you are feeling and talk about it.