I disagree with this. Michael was smart enough to know that Sonny's temper was to blame for his death. Tom warned him not to leave, he tried to stop him, and sent the bodyguards after him. Sonny's temper was so bad, no one could have stopped him. Don Vito clinches it for me when he says that "I never believed you were a bad consigliere, I believed Sonny was a bad Don, rest in peace."

As far as Kay's abortion. Sure he might have wondered how Kay got out to see an abortionist, but I don't believe he blamed Tom. Where do we see that? He doesn't kick him out of his life as he does to Kay. If he believed these things were Tom's fault, I don't believe he would have ever kept him around.