I see absolutely nothing out of the ordinary here. This is perfect.
No they don't. If you're seeing it like that, I suspect it's a problem with your screen, or lack of calibration.
By the way, please don't waste your hard drive space by working in 16-bit. It's completely unnecessary.
May I ask what quality level you chose when saving the jpeg files for upload here?
Sorry, it won't work. If you take away the wall and the shadow, the hair will just look inexplicably squashed flat on that side.
Anyway, it would be impossible to take away the shadow, I'm afraid.
Good! Now keep tweaking the gradient so that the colours match the existing colours down the right-hand side of the subjects as closely as possible. The better match you get down there, the easier your masking task will be.