Living in an unsafe neighborhood affects Ponyboy's development because it shapes character. If he didn't live in this neighborhood, he would probably be super friendly and have a good education and he probably would not want to smoke. But being in the neighborhood he's in, he's forced to be tough and strong. Also because he is a greaser, he has to participate in rumbles and fights.
The church affected Ponyboy's and Johnny's life. One reason is that was where they spent most of their time when they were fugitives. Also, it affected their lives because if there was no church, then Johnny and Ponyboy would not have saved those kids, and that would mean that Johnny would have never died. And Johnny's death really impacted Ponyboy's life.
When johnny dies not only is Ponyboy affected but the whole gang. After Johnny died, Dally left the hospital in a huge fit while Ponyboy acted like he was crazy. According to the book, Pony states, "That still body back in the hospital wasn't Johnny. Johnny was somewhere else-". Also after many weeks after Johonny's death, he lost it. He started failing school, losing things and running into things.