OP, look at it this way, you are probably unhappy at home and I'm sure your daughter can see it. So you make a clean break from your wife and learn to be happy again. Your daughter gets to see you (and probably your wife) happy and hopefully down the road in healthy, happy marriages.
You'll be a better parent if you walk away from a bad situation and move forward. Your life isn't over and chances are your wife will eventually remarry anyway.
Try to look on the bright side.