If I understand your question #1, you have two versions of an image -- a final version that you like, but you don't know what adjustments were done to it to get it to that state (lets call this one Image_A), and an initial version, either a RAW file, or SOOTC (straight out of the camera) JPG (lets call this one Image_B).
My approach to tasks like this is to bring both images into PS on separate layers, with Image_A on top. Set the blending mode of Image_A's layer to either "difference" or "subtract". Then, as you see fit, insert adjustment layers between these two layers with the goal of reducing the brightness of the difference image to zero everywhere.
One of the difficulties in the above procedure is that for some images, certain color differences will be much more visible than others. For example, is that bright red that you see in the difference image really more significant than an area of blue that doesn't jump out as much to your eye. To minimize such issues when making straight tonality adjustments, put a B&W adjustment layer immediately above the layer that contains Image_A in subtract blend mode. With this, you only need to compare brightnesses, not both brightness and colors simultaneously. However, occasionally, toggle the B/W conversion on and off to make sure you aren't making some gross color error.
Usually, it doesn't take long to get a close, but not perfect match. To further refine your approximation, add a "levels" adjustment layer over everything, and then move the RH slider in the levels dialog box substantially to the left to brighten the difference image. Doing so will allow you to see the effects of smaller and smaller tweaks to Image_B.
Another problem that often occurs is that Image_A will have had some sharpening applied to it so that when you form the difference between it and the tweaked SOOTC image, there will be bright halos around every object with a sharp edge. The way to get around this is to first work on major areas of color and brightness, and then go back and tweak the sharpening of Image_B. In my experience, the easiest way to do the former is to start by simply blurring both images a bit. You then won't be distracted by the halos, and once you get the major areas of the image close, you can turn off the blurred versions and then work on approximating the sharpening used by minimizing brightness and widths of the halos.
You might think it's a PITA to work using this difference technique, but my experience is that it is much more logical, systematic and sensitive (and ultimately, faster) than trying to do the approximation by eye.
HTH,
Tom M
