I could suggest several more important events in A Separate Peace. Consider the invention of blitzball, which provided Finny with a tailor-made outlet for his physical abilities and allowed all the boys to be actively involved in an activity which couldn't be won (parallel to involvement in a war?) but in which one could refuse to accept the ball (in contrast to the war, where orders are given and must be followed). Consider Leper's decision to drop out of school and enlist, and then his decision to go AWOL (absent without leave) and his mental breakdown after he had experienced actually being involved in the war. Consider the "trial" when Brinker is prepared to prove that Gene purposefully caused the branch to bounce so that Finny fell out of the tree.
A Separate Peace is very carefully written. Almost every event of the book is wrapped in layers of significance and meaning - your challenge is to choose what you consider to be only five as the most important events.