It's impossible to tell on the basis of just one photo.
Don't worry about it for now. If I see a pattern of darkness in your raw class posts, I'll let you know.
No, that's right. That's exactly how it's supposed to work. You can make any modifications you want, and simply save and close that PSB file, and it will update in your PSD file.
Always use cloning if you can.
But if you feel it's not an option here, you can try this Channel Mixer layer:
R +100, 0, 0, 0
G +79, 0, 0, -9
B +61, 0, 0, -12
(Make sure you enter those numbers in exactly the correct order.)
Yes, that definitely is possible, but if that was the case the Window>Workspace> menu would say "Reset Laura's workspace".
I think it's more possible that your workspace got lost in an update, I fear.
You didn't post a SINGLE photo in class. I sure hope you're not telling people "I took Damien's Raw Class but it didn't help me". Of COURSE it didn't help you, you didn't post any photos.
Take the damn class again, and USE IT THIS TIME.