Underestimating the wife
When Hermann Karlovich thinks about his wife, he barely respects her. He is so convinced of her inferior status that he believes a lie about her. He believes that she worships the very ground he walks on, and when one day, he walks in on her having sex with her own cousin, he maintains the perplexing belief despite all evidence. This is a signal to the reader that his underestimation of the wife is actually a symbolic reference to his delusional perception. He needs to believe little about her to make himself feel great.
The chocolate factory
The chocolate factory is a symbol, too. Perhaps it is also a reference to Hermann's ability to "pump out something sweet," so to speak, in terms of his own self delusion. He is convinced of a sweeter version of reality than the one that really exists. His success in this endeavor gives him a false sense of confidence. This is not the genius factory owner that one might find in a Roald Dahl novella; this is the talent of self-delusion taken to its natural limit.
The "doppelgänger"
The doppelgänger represents an encounter with his dark side because Hermann feels they look exactly alike, but the other man, Felix, does not see the resemblance at all. The idea here is that Hermann is projecting onto the man. In the end, this encounter will bring about his reckoning, but for now, it allows Hermann to calculate a plan that will be his demise. Put plainly, his delusional perception is a hubris that makes him encounter reality poorly, and this makes him believe he will get away with a murder which he will not get away with.
The murder
The murder is quite peculiar from a symbolic point of view. One would think that Hermann might murder his wife, since he walked in on her having sex with her cousin. But in a darkly humorous twist, he kills his doppelgänger, a symbol for his own tendency for self-destruction. The murder shows that he is absolutely convinced in his own warped point of view. He is convinced that his wife would never cheat, despite witnessing her in the act, and he is convinced that Felix looks just like him when in reality they are different.
The reckoning
When the police come, symbolizing justice, judgment, and reckoning, they prove to the reader and to Hermann alike that his perception is only relevant until he becomes the suspect in a murder case. Then, his opinions and his tendency to explain away reality will not help him. The reckoning comes and he is found guilty. In delusions of grandeur, he entertained false ideas to the point of murderous, Machiavallian plots. The reckoning shows the tragedy of delusion. His opinion about reality is only so important after all.
