In Twilight, how is James affected in the falling action of the plot with Bella?
You have asked more than one question, so I'll answer your first:
James dies in the falling action. The climax of the story could be said to be the scene in the ballet studio where Bella goes to meet James (and, presumably, her death). The battle that ensues between Bella/James/Edward and the Cullen clan is the major event; the falling action is the resolution of that battle and Bella's recovery from her injuries. The Cullens kill James, so that is how he is affected.
James get killed by the Cullens in the falling action. This was from James trying to kill Bella and luring her into the studio. The Cullens kill and set him ablaze so he cannot come back
In the falling action James is killed by the Cullens. This was in response to the climax which was James luring in Bella and eventually almost killing her with biting her and infecting her with his venom however Bella is saved by Edward. And the Cullen's take care of James by ripping him apart and burning him up so he does not come back to life.