The most unbelievable part
I know this film is satire, but the one part i find unbelievable is how Walter could be convinced to kill his wife within a month or so. Even given that he's a chauvinist, to actually kill another person is not something most people can do - even if they hate the person. And this wasn't even someone he hated. He apparently really did love his wife.
What would the men's association do if Walter had refused? I imagine they would have to do something with Walter to keep him from going to the cops. How would they explain it when the cops (not Stepford ones) started investigating the missing people?