Does the first segment realy depict reality?
First let me state my overall interpretation of this movie briefly. I believe the first segment contains a weak suppression by Fred of his guilt of murdering his wife, while the second segment contains a strong suppression (fueled by the sleeping medication). The middle part in jail is reality. I assume some people may disagree with this. I only state this as to give an impression of where I stand.
Now if one believes the first segment is indeed fantasy, like I do, how can we be certain about the truthfullness of it? We understand Fred creates these fantasies to suppress his feelings of guilt, so why should we believe anything he comes up with? For instance, wouldn't it be logical to assume that Fred makes himself believe that he had reason to kill Renee by making her go cheating on him? We have no evidence Renee actually was cheating on him, let alone she did porn movies. What strikes me is that everything in this first segment pleads for Fred himself: there are lots of excuses for him that would count as extenuating circumstances. Since it is the fantasy of Fred himself we never actually get to know what the real reasons for this murder were since we can assume that Fred tends to be biased towards himself.
So was there realy a Dick Laurent? If so was he indeed a porn director or was he the man Renee cheated with (if at all)? In short: what exactly can we believe in these fantasies of Fred. Everything points toward Renee doing porn, but couldn't this just be Fred's depiction of her cheating? Or maybe even his jealousy bordering on paranoia towards his wife? My view is that we can never be sure about the real reasons behind the murder. Moreover, we cannot trust the narrative of Fred's fantasies so that many questions we might have be left unanswered.