I would say that Macbeth would be described as a pawn of fate. He starts out as a great warrior that everyone is impressed with. His King promotes him to Thane of Cawdor and that is all free will. However, once he meets the witches, in my opinion, he becomes a PAWN of fate. The three ugly sisters make prophecies and he follows them. While he still has free will, your use of the word PAWN causes me to think that he would have to be judged as such. The witches make suggestions, but he follows them. It's true that these decisions are up to him, but the witches are manipulating him into doing things. Once they get him started, others, particularly Lady Macbeth, are able to influence his decisions. At the end, he falls victim of the witchs' prophecies and there is nothing left for him to do but succumb.
Personally, I feel that Macbeth, by attempting to become an agent of free will; became a pawn of fate. The use of theatrical metaphor clearly shows that Macbeth attempted to lead his own life. He tried to seize control of the script of his life, to write it in accordance to his desires, in clear knowledge that it would end up disastrous. His return to the witches and murders shows his attempts to rewrite the "script of his life" into something that answers his needs. But all he succeeds in doing is turning his life into a sinking nightmare of "strutting and fretting", becoming a pawn of fate.