Question

who did he blame for what had happened to him

Answer 1

I personally think that Macbeth is the one to blame. He could have resisted the witches' prophecies and made choices that went against them, but he decided not to. HE killed Duncan, not the witches, not Lady Macbeth. He did. HE sent the murderers to kill Banquo. Even though everything was prophesied by the witches, Macbeth was the one that followed through on them, and he is to blame for everything.