Look at all of that awake time with the screen off. Are you listening to music with the screen off during those times, or on a phone call?
Have you considered going a day without the FitBit, just to see if that changes the battery usage?
I wouldn't worry too much about "Android OS" - unfortunately, that can be just about anything, but I suspect that you have something that is holding the phone awake in the background. If it isn't music playing or the FitBit, you'll just have to find what that is.