I disagree. There's interest in the whole sky; and cropping off the top would unbalance the composition. It's a fine shot as it is and I'd leave it alone.
Same here. Even if you think of it as 'dead space' around the focal points of the composition, if it was not there the focal points wouldn't have as much impact.
I'm yet to get a sunrise/set that I'm proud of, but this is great. What sort of shutter speed were you shooting at to get the water like that?