I agree with Momrek, the crazy act is entirely fake. It may not be that the producers set it up (although clearly they're not above that sort of thing if they wanted a fake-divorce storyline), but I have no doubt that Heidi and Spencer concocted this to get more air time. They wrote a book about how to be famous, for goodness sake. Spencer bragged about playing "the villain" on talk shows and in "I'm a Celebrity." This is their franchise.
I do believe that Spencer is a total tool, that he's controlling and his alienated Heidi from her family, but I think he's only "deranged" when the cameras are rolling.