Upload & Sell: On
Yes, posting your own separate thread is generally going to get you more feedback. In addition to that, MATA is more of a community where you can get feedback if you want it, but we're not very focused on C&C... more on sharing. But the expertise and knowledge in that group is very, very deep and broad; and if you're looking for people to guide you a little, then that's an excellent place to start.
Masking out a sky is not for the faint of heart. Essentially, what you're doing is digitally following the outline of each aircraft with a pen tool, or some other tool, to "cut" the shape of the aircraft out of the sky. It's not difficult, but it's very, very time-consuming. Then you can keep the aircraft and the sky on separate layers, and adjust each independently. The #6 image just seems cool enough to be worth the effort, because I think you have a real winner there.
For #2, it's a lot easier. If you'd like, I can do a little retouch of it and post it here in the thread to show what I mean... just a little brightness and vibrance/saturation, plus some contrast and some sharpening, and Bob's your uncle. That's a 30-second editing job.