I think a d12 HD should be reserved for non spell-casters, especially since you have a very generous amount of healing ability, and there are paladin spells out there that can grant you temporary hit points. I also think that the high base Will save is a bit much given that you already Divine Grace working for you.
I might suggest you keep the paladin's spellcasting feature based on wisdom. That way you could create a feat to allow your paladin spellcasting to be charisma-based instead... a feat that lies in contrast to how the Serenity feat makes your charisma-based paladin abilities key off of wisdom instead. That way, a standard paladin's abilities would remain divided between wisdom and charisma, until one of two feats were taken to focus those abilities on just one of the two ability scores.
Don't know what to say about the base features of the class... except that I would try confining the abilities gained at each class level to one, starting when the paladin's spells become available.
Although... you could make up for it by giving your paladin a caster level equal to his or her class level, which in turn would increase the minimum caster level of paladin spells for the purpose of crafting... which would allow you to reduce the spell level of some paladin spells by 1 and bring in a few spells from other class lists to give the paladin more flexibility. (
Here's something I recently did to that effect.)