Much better sky, but I preferred the previous landscape ;)

Thanks guys! As above, I did take your advice to heart. Hoping this result is a little more emblematic of what I want to express here.

I love the landscape.

I agree that the sky would look better without dithering and a dozen color gradient. Also needs hue shifting in the light tones. Example for both points.

Honestly I feel like this is one of those cases where low color count is responsible for making it kind of impossible to do what you want to do here.  I would increase the palette to 16 or even 24 colors if only to make the gradient in the background smoother.  The visual noise caused by the dithering is responsible for destroying a lot of the depth you're trying to create here.  Alternatively you could see how well it works with no dithering at all.

I like the palette and concept a lot, though!