I really liked David Dastmalchian's performance. Jack is a charming enough "aw shucks" Midwestern goober, but as the film goes on you see that this is a persona; behind the scenes Jack is focused on/worried about ratings, etc. But although he is exploiting Lily for ratings, he is concerned when Christou is sick and when Lily says things that hit close to home. He is a consummate showman so doesn't get too emotional when Christou refers to "Minnie," a secret nickname he had for his wife or when a possibly-possesed Lily mentions having met him before. But we still see that these things bother him.
David Dastmalchian has eyes that are so dark they're almost black, which gives them a depth that somehow makes him look more innocent/"softer" while also being harder to read.
Some of the special effects near the end (when things got really weird) kept the 1970s "fakeness" so things looked like they weren't really happening when they were.