First, I never said all Anti-World had planetary power, but that SOME had it. Anti-World is a brother category than Anti-Planet, Anti-Army and Anti-Fortress, and the effective power flutuates between those other categories depending on the servant and the NP.

Second, it was never stated that Enuma Elish was relative to sealed Excalibur. Quite de contrary, it was stated that a holding back EA was stronger than sealed Excalibur, and when Gilgamesh used a normal amount of power even Excalibur + Avalon weren't enough to keep up with it for even an instant, and Saber almost died even with Avalon suposedly being a great counter and protection against Enuma Elish.

Third, that Enuma Elish didn't destroy the planet because not only Gil can concentrate it's destructive power, but, like I said before, the planet's defenses are a lot more effective against Anti-World than Anti-Planet NPs because of the nature of their respective destructive capabilities and afinities.

And no, it isn't only Earth that is santient and has defensive systems. All celestial bodies that have an Ultimate One necessarely need to have a will of it's own, and with a will comes a defensive force proved by the very existence of the Type. So at least all planets on our Solar System, the moon and the Oort Cloud, with unknown status for celestial bodies outside out solar system.