AWT, I'm so sorry you're stuck in this really crappy situaltion. No matter which decision you make, there will be pain & suffering involved. If you decide to stay in the marriage and your wife doesn't change, your morale & self esteem will slowly be whittled down by the daily barrage of put downs and nagging. If you leave her, you will have to endure the costliness of divorce, custody battles and worst of all, the confusion and heartbreak your daughter will be put through. I'm also the parent of a little girl and I know what a burden being faced with a seemingly impossible decision feels like.
I want to mention something for you to consider. You and your wife have similarities to my own parents. My father was an easygoing & passive man. (To this day, I have not once heard him raise his voice.) He will do anything to avoid conflict. My mother was the polar oppisite. She was brash, turned everything into an argument and was verbally & physically abusive. As the recipient of physical & verbal abuse, I can tell you that verbal abuse can be just as harmful as the physical! As a child, I thought my father was a kind and sweet man. All of my life I've had so much anger towards my mom for mistreating my dad. After having listened to Stef & gaining some self knowledge in recent years, I realized I have even more resentment towards my dad for allowing my mom to mistreat us. My parents are still married today. I wish my father had divorced my mom the first second she laid her hands on her children. I will spend the rest of my life trying to undo the damage she inflicted on me. In my opinion the sanctity of marriage doesn't mean shit when abuse is present. Sorry for going on, what I'm trying to say is although marriage is of course ideal when raising a child, if the parents are incapable of respecting each other (which according to what you have said, your wife seems unable to do so at this time) then it is in the best interest of everyone to dissolve the marriage.
There is a shimmer of hope since your wife agreed to do therapy even though reluctantly. I really hope you can open her eyes to her behavior and the damage it is doing to everyone. I also hope you put your foot down when it comes to her raising her voice to your daughter. That should not be tolerated. Good luck to you and congrats on taking the first steps to fix things.