Who is the god of evil? Jack feels emasculated, at first he only feels moderately insecure, so he imagines Bob there to help cope with his insecurity and anxiety about his actual testicular cancer.
We are not watching Tyler save Marla in this scene, we are watching Jack leave the hotel completely alone, yelling at the paramedics franticly about how Marla is infectious human waste hence the use of the 3rd person when Marla is yelling at the paramedics.