Great. In that case, you don't need to do anything. Just provide the photo at the exact size your camera captured it. No cropping, no resizing.
Have you finished editing the photo?
If the lamp really was the light source, two things would happen.
His legs would be very dark, because they'd be in the shadow of the book
His shirt and face would be very golden, from the lamplight, you know?
Sorry, I don't understand this question. Isn't black what you want? That's what the eyedropper does, it changes the colour of the point at which you click, forcing it to be black.
I'm so sorry, I've got no clever ideas. I'd just add a Solid Color layer of skin-ish colour, set to "Color" blend mode, and paint it over the dummy to disguise it slightly.
Ok, the rest should be fairly straightforward masking on the black Solid Color layer, yes?
Inevitably you're going to lose some strands when blackening. And inevitably some tips of hair will change colour a little.
Is this ok?