Gary Troup and his thriller novels that use the in-show world's characters, businesses and stories draw heavy influence from Dan Brown and The Da Vinci Code. They both take real life organizations and stories to create stories that are fictional, yet almost believable.
Troup would not have been killed if John hadn't stopped him.
Troup knew too much to have the Island allow him to live. His research on the Valenzetti Equation would have led to knowledge of the DHARMA Initiative and he would have recognized the logos and other happenings around the Island. There is a reason he was one of the first the Island decided to kill.
Was not meant to be on Flight 815, but changed his plans so he could be on the same plane as Cindy to surprise her.