Question

3. Is Macbeth a tragedy of fate or of character? In determining your position on this, consider whether the witches play a central or collateral role in shifting the ambitions and actions of the play’s characters.

Answer 1

the witches play a central role in the shifting of ambitions because without their prophecies, Macbeth would not have felt the need to kill Duncan in order to fulfill the telling of the witches and to become the king of Scotland. Also, he killed Banquo out of fear that the witches prophecies might come true for him as well and that Macbeth would no longer maintain his kingship.

Answer 2

It's a tragedy of character. Both Macbeth and Banquo were shown their fate but only Macbeth acted out his baser instincts to get his ambitions.
note: the above answer is correct for your other questions.