I don't think Michael was fleeing to Florida because of the hits. Michael had a scheduled set of meeting with Roth and the other investors in Cuba. The NYC meeting with Frankie was an irritating setback to him because it was interferring with his work into getting into the Cuba gaming. I do believe that Michael may have left several hours earlier than he planned. Perhaps, to prevent further hit attempts by off-tracking the potiential traitor from knowing his schedule.
I think that the hit attempt occurred after's Anthony's party was because it provided a better window of opportunity to get the hit men on the estate. With the caters, cooks, set-up crews, etc, the guards will be more lax allows someone onto the grounds. I also do not think Pentiangli's physical location (rather in Nevada or NYC) is important (impt)for Roth to make anyone believe that Frankie is responsible for the hit.
Actually, I don't think Roth really gives a damn who Michael believe ordered the hit. Roth took a shot in doing away with Michael without undergoing long, drownout sceduled meeting with him. Roth had no intentions in doing business or sharing the wealth of Cuba gaming with Micheal.
Roth has been in the rackets before Michael was born. He is a Jew in an Italian clad underworld and has outsmarted them all. He had no doubt that he could handle Michael.