one
Of all the characters in Hamlet, the one that play acts the most is Hamlet himself. Why?
Look at his surroundings. His mother thinks he is mad because of his father's death and her quick marriage to Claudius. That has just enough truth for us to give it a very quick nod.
Polonius (who was once a very wise man -- he had to be since he was a trusted councilor to Hamlet(Sr) ) thinks it is his daughter who caused the madness. Every young man (again remember Hamlet is a teen) endures the lasting sadness of a first love unfulfilled. Perhaps even driven mad by that first love. Polonius may be a fool, but his observations should not be completely ignored.
While on the subject of Polonius, you might want to make use of Hamlet's exchange with him. I remember that scene being a bit longer than what I just read beginning on line 165 in Act II Scene II. It should be longer than 30 lines, but there is enough there to get the idea that Hamlet is covering up something by acting the mad one.
So Hamlet has to resort to subtle subterfuge to get at the truth. And the directions he gives leads us to see that he knows quite a bit about the art of playacting.
Claudius is uncertain, but he's willing to test just about any theory that comes his way.
Is Claudius irreligious? How can he be when he attempts to pray.
Is Claudius totally without feeling? How can that be? First of all he shows some slight affection towards Gertrude in Act II Scene two after Rosecrans and Guildenstern have been dismissed.
Two
I can't do anything much between the similarities and differences on Fortinbras and Hamlet. What you find on the net should be able to guide you. I have never thought much about Fortinbras but a bit of his nature is revealed in Act II Scene (you've just been there) when Voltemond tells Claudius what has happened in Norway and the anticipated trip to Poland. I can only think of Fortinbras in terms of the ending when he and Horatio are the only main characters still alive. That really is not much to go on.
