Turnbull,
Your third point is way too much assumption Fredo did NOT say Ola took him to the show, he said he "TOLD HIM" about the show. then said Old Man Roth wasn't into that kind of stuff. I do agree with you guys that Ola and Fredo knew eachother from Vegas, how close, I have to think he wasn't close enough to go on the boat back to the us WITH ROTH. Roth wouldn't be so stupid as to be seen leaving with Fredo after killing Mike. Ideally which is what they were hoping to accomplish on that trip. If Roth and Fredo were working together, they would lay low for a bit incase Tom Hagen or the Mother tried to seek Justice somehow. Remember Tom was VERY loyal to the family. The Corleone's were all he knew as he was homeless and very sick as a child when the family took him in, and they always treated him like a smarter less vicious ally and a son. I really think Tom didn't know where Fredo was just that he was safe. Fredo probably just went home by himself and hid out for awhile