Jansy asks "why did Kinbote have to hide away the cards with the poem," and wonders when Kinbote became an invention of Shade's.
Dear Jansy,
My theory is that Pale Fire is Nabokov's re-invention of Robert Louis Stevenson's Dr Jekyll and Mr Hyde, and that Kinbote and Gradus are suppressed alternate personalities of John Shade who are able to take over his consciousness following the stroke described in the fourth canto. The idea that Shade or Kinbote is the inventor of the other is another theory entirely, a theory that Nabokov himself ridiculed.
The insane John Shade ("Kinbote") has to hide the poem because Sybil and several professors want to get it away from him, fearing what he might do with it.
After Shade's personality is "killed" and the alternate personality of Kinbote emerges, to his wife and colleagues it seems that Shade has gone completely mad. He is hospitalized for a while, but manages to escape. All this Kinbote narrates as if he were the King of Zembla escaping a revolution.
This explains the chronology problem that you mentioned. It seems that Kinbote's perception of the present (during Shade's hospitalization for example) is projected into the past (the Zemblan revolution). Possibly because he was "born" when Shade was 14 or 15, his perception of time is distorted into a kind of fugue. Nabokov may have been aware that the periods when an alternate personality emerges into consciousness used to be called a "fugue state," experienced by the dominant personality as a blackout.
Carolyn