Timelines are fun, but frustrating because we have to deal with three movies that span a century, plus changes of character and sloppy writing. You've got the approximate dates right when the movies make clear when a particular scene occurred. But, I believe Michael was in Sicily much less time than you suppose--four years is far too long for a Mob war.

I constructed this timeline for Michael's Sicilian sojourn based strictly on the novel, which also suffers from sloppy writing but at least doesn't have a century to cover:

http://www.gangsterbb.net/threads/ubbthr...true#Post580389