Blocks:

Calcrete - Spawns in new moon biome, is very hard and spawns on surface

Hardened Calcrete - You can harden calcrete using moon rock to get it and it is very effective against explosions of creepers.

Aluminum Moon Ore - Aluminum ore on the moon

I made mobs also jump higher on the moon, Now, you'll suffocate on the moon if you won't have an oxygen helmet which is new type of helmet made out of plastic dirt, steel aka carbonic iron and black stained glass.

I did not find the problem that causes spawning under ground on the moon. Sorry.

That's it, thanks for playing, Enjoy! Peace \/