I think we agree that Jerry Lewis’ The Nutty Professor is far more than “the mere residue of a well-publicized show business feud.”
Jerry Lewis, along with Charlie Chaplin and Orson Welles, was one of the cinema’s great solipsists. Thus, Charlie Chaplin playing Adolph Hitler (Adenoid Hynkel) in The Great Dictator tells us as much about Chaplin as it does about Hitler. Likewise, Orson Welles playing William Randolph Hearst (Charles Foster Kane) in Citizen Kane reveals more about Welles than it does about Hearst. And Sergei Eisenstein’s Ivan the Terrible (played by Nikolai Cherkasov) is roughly one third Joseph Stalin, one third Ivan, and one third Eisenstein himself. The narcissism of Buddy Love in The Nutty Professor is more reflective of Jerry Lewis than it is of Dean Martin. So it goes in le cinema auteurist.
Therefore, to say that The Nutty Professor’s Buddy Love is mainly a poison pen portrait of Dean Martin would be a mistake. Just as it would be a mistake to say that Buddy Love has nothing to do with Dean Martin. I think Andrew Sarris hit the nail on the head when he said that in The Nutty Professor, Jerry Lewis was recreating the “dynamic” of the Martin/Lewis screen relationship – particularly those Martin/Lewis films where Martin played a self-absorbed cad and Lewis played his adoring “stooge.”
You and I agree that “Julius Kelp/Buddy Love were just manifestations of the larger sensibility that conceived the Martin/Lewis personae in 1946,” that larger sensibility being Jerry Lewis’s. Buddy Love is not the real Dean Martin whose unpretentious, relaxed, and “fundamentally detached” attitude you so aptly describe; he is the imaginary screen persona – let’s call him “Dino” – conceived as the smooth adult counterpoint to Lewis’s hysterical “kid.” Martin & Lewis’s Dino had to be worldly and corrupt to highlight the kid’s child-like innocence. Lewis’s Buddy Love provides a similar counterpoint to Lewis’s Julius Kelp in The Nutty Professor.