I only see on the UESP where Turn Lesser Undead, Turn Undead, and Turn Greater Undead are affected by the 25% increase to undead level that can be turned. Are these the only three spells, or do the Repel Undead spells, Circle of Protection, and Bane of the Undead (etc) gain the effect as well?

I would think they would, but it's not mentioned in the UESP or reflected in game.

Nevermind.

Apparently they are all affected by Necromage, and I learned that Circle of Protection can effect Undead up to level 55! Yowza!