I agree with some of what has been said. I agree that Michael suspected Fredo, which is evident during the banana dacquiri scene. And I agree that Michael was sickened by the confirmation of the betrayal at the Superman show. I also agree that the kiss was an emotional gesture made from anger.

However, I don't agree that Fredo's fate was sealed in Havana. I think that Michael felt that Fredo had been led astray by Roth and his people. It was not until Michael heard Fredo's little tirade in the boathouse that he decided to kill Fredo. When Fredo ranted on an on, revealing the depths of his frustration and resentment, it became clear to Michael that Fredo would be a constant threat to the family, and would have to be eliminated.