As I mentioned, I suggest ability burn caused by the Psychocarnate's class features recover at an accelerated rate somehow (possibly 1/level/hour). It doesn't have to apply to ability burn caused by other sources.
Highest level power known + Wisdom modifier is ok, but you should explicitely state that it goes to a maximum of 9th level powers, for the reason I mentioned.
Edit : I know its late to ask, but a PEACH on the Apostle of Madness would be appreciated.