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.
The exact dialog from the script is:
FREDO
JOHNNY OLA told me about this place.
He brought me here. I didn't believe him -- but seein' is believin', huh?
I have to think he wasn't close enough to go on the boat back to the us WITH ROTH.
Then how did Fredo get to NY in the same 48-hour-or-less time frame that Michael got to Vegas?
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.
Roth's plan was to have his pals in the Cuban government have Michael assassinated in a government car on his way back to the hotel after the Presidential New Year's Eve party. Neither Roth nor Fredo would have been anywhere near that government car when the assassination occurred. The major purpose of Roth's speech at his birthday party, promising to turn over his Havana interests to Michael, was to establish an alibi for Roth--"what, me assassinate Michael? Why, I loved the kid like my own son. I was gonna turn everything over to him...just ask any of those thugs who heard me say it at my birthday party.
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
Then why did Tom say he was in New York, especially since "home" to Fredo was the Tahoe estate?
