I would also point out that wanting a divorce and wanting out of the cult are two seperate issues. perhaps your major concerns arnt exactly what you think they are.....
_Morpheus is exactly right on this issue. You need to figure out what it is you want/need and go from there. I want out of the cult more than anything, but I could never think of leaving my wife (who is currently hardcore). I want/need her, but I don't want/need the religion. What is it that YOU need/want? From life? From your spouse? Don't confuse getting what you need/want with being selfish.
But back to your original question. Everybody has there faking limits... I myself am doing it right now. Some might call fakers "spineless", "cowards", and things like that. I prefer to think of it as playing it safe and waiting for the right moment; damage control, if you will.
It is very hard sometimes and you can lose your self-identity from time to time. It is weird to not believe a word of the religion, and still be trapped into "giving the full show." And its even harder to question belief in a "god" and be involved in any religion at all.
Some people need to quit cold turkey, and that's fine if that works for them. Others need time to strategize, plan, and organize and exit or a fade. But once the scales fall from your eyes, it will be very hard to fake it whether its for a few days, few months, or a few years.
Don't do anything quickly in the "heat of the moment" without clearly thinking things through. Baby steps are the best way to start, I have found.