I don't think he was ever boss but he ran the entire West Side and parts of the South as most of his contemporaries were being locked up so his reach was pretty vast. However, I am pretty sure that Aiuppa took over as boss once Cerone was imprisoned in 1970.
I agree completely. Fif's crew was essentially what became the Cicero Crew, only at that point, they ran the first ward, loop and Chinatown. When Fif passed, they cut up his territory. Fif's main lieutenants aside from his brother Frank (who controlled rackets in Milwaukee) were Turk Torello and Joe Ferriola. Torello took the spot in Cicero, then when he passed, Ferriola took over.
Aiuppa was essentially the acting boss by that time. Fif was always just a CAPO and below Aiuppa.