#2 - I can`t quite say I understand what your problem is, but maybe this will help - have you checked if you`ve locked the layers transparency? Maybe that`s why it`s retaining hard edges, b/c with this option on you can paint inside the shape of that layer, not outside of it. Also, have you masked the layer?
I had locked some layers before yes, but im not painting on them layers now, if i paint over the top of everything on a new layer, its like these little gradients interfere with it. its hard to explain.
and i cant replicate it, it just happens every now and again on certain images, i have no idea how it does it.
I see some of the banding as well in that image. Unfortunately I'm not sure how to fix it. I get it sometimes too on my screen, but usually just ignore it. It's not a huge issue as it is barely visible (especially with such dark values); if anything it just adds a bit of texture. I sometimes notice that it is more or less apparent at different zoom levels (like some weird percentage vs say 100 or 50%).
Your screen might also not be properly calibrated--those values are pretty dark which is why a lot of people can't see the banding. The screen I'm on now I know makes dark values a touch lighter, which is probably why I can see the banding.
"Complacency is the womb of mediocrity. " -- Jason Manley
"If you always put limits on everything you do, physical or anything else, it will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them." -- Bruce Lee
Best thing to do to avoid banding on gradients is to make sure "dither" is selected for one. The other thing is to add a little bit of noise to the gradient. Like 2-5% should be enough to break up the uniform pixels yet keep a smooth gradient. The gradient will be more optically mixed than value mixed.