1. I do not think that Neil would have committed suicide, but I do think that he would have been unhappy and uncomfortable for his entire life. He never liked what his father had planned for him to do in life. He wanted to take up acting and his father was not impressed, he only wanted his son to become a doctor and provide for a family. Mr. Keating only took part in Neil's life when he told Neil to be his own person and pursue his dreams. This may have caused his suicide, but overall, Neil was never happy.
2. I believe that Todd is the most brave of the Keating boys. He is very shy throughout the movie and barely ever talks, but in the end he stands up for what he believes. He believes that Keating is a good teacher and teaches the boys good ways to get through life. On the other hand, Cameron was the coward in the film. He never feels like it is safe to go with the boys to the cave for the Dead Poet's meetings. In the end of the movie, Cameron is the one that turns in all of the boys that attended the meetings and they were all told to sign for the resignation of Mr. Keating. If Cameron would not have been so scared of everything, Mr. Keating most likely would still have his group of boys that followed him.
3. I believe that Keating did place the poetry book in Neil's room. He knew that Neil was the one ready for the challenge, and he did not want to be the one to stop him from chasing after what he wanted. Even though Keating knew that it was not the best idea, due to the administrations issues with reckless behavior, Keating believed that the boys needed to find their true potential.