There are a couple of issues, Christina. You could have maintained the desired ISO and used a faster shutter speed by using a larger aperture, so long of course that you would have still maintained the desired depth of field and assuming that a larger aperture was available.
However, using a faster shutter speed would not have separated the ducks from the water. This image reminds me of shooting an image through frosted glass. The only way to get greater separation between the frosted glass and the subject is to remove the glass. In your case, the bright water is similarly between the camera and the ducks. Our eye tends to see bright objects first, so the only way to truly make the ducks stand out is to shoot them without the water or with significantly less water. The moral of the story is that it's inadvisable to try to make something of a scene that can't be made.
Again, it's generally best in my mind not to try making something of a scene that isn't there unless you are being really creative, such as the images that Sharon regularly makes that bear little resemblance to the physical scene. If you want a high-contrast image, shoot a high-contrast scene or at least a medium-contrast scene. If the scene is gorgeous and has little contrast, exploit that characteristic to your advantage rather than eliminate it.And in the case of photographing in low contrast situations, ie; foggy days, could I not change the tone curve in my camera to a high contrast curve to fix it right then and there?
As Dave pointed out, the histogram can be used for things other than exposure compensation, though like any tool it has its limitations.I was under the impression, that the understanding the histogram, beyond its use for exposure compensation could be useful for other photographic parameters/variables but perhaps not?
Sorry that I can't address your other questions. I'm interested in seeing other responses to all of your concerns.