I am in total agreement with your assessments of the changed characterizations of the Stan and Lilith roles. In the original film, there was a degree of ambiguity that made Tyrone Power and Helen Walker more interesting. Audience members were unsure if Pete's death from alcohol poisoning was accidental or deliberately planned by Stan. Lilith was not depicted as pure undiluted evil from the word go which made her betrayal of Stan much more jarring.
My other problems were related to the other carnies. In the original, there was a feeling of fraternity among the carnival members that is woefully lacking in the remake.
The casting of Rooney Mara as Molly may have been the worst call since Betty Field was slated for the role of Daisy Buchanan in "The Great Gatsby." There is no romantic chemistry between the Stan and Molly characters in the remake. Likewise, Toni Collette does not fill the role of the adulterous Zeena nearly as well as Joan Blondell did. Of course, Blondell had a reputation for enjoying male companionship offscreen as well as on.
I am not sure if the remake was more faithful to the source novel or not. I did miss the sequences of the original film that were set in Chicago.