unforunately, no, there is no way to make it for one single map. sorry!
also, yes, it would show throughout the whole 'cycle ' no matter what colour you made the sky etc.
for your moon, you'd need to put it into feralheart >> media >> textures to have it in-game, i'm pretty sure! unforunately, nobdoy would see that moon texture/ and or sky texture unless they had the same textures as you! just a little heads-up.