A FISA warrant, even if one was in fact issued, does not make wiretapping legal IF 1) The warrant was obtained through perjury or some other fraud on the court; or 2) If the scope of what was obtained exceed the scope of the warrant.
Your item 2) applies, because 0 went beyond the scope of the October FISA; took it from just looking at a bank, to looking at President Trump’s comms- both home & office.
President Trump said that it is a FACT that Obama tapped his phone lines.
He does not mention FISA or judges or any court.
It was Obama acting alone.
Those are the facts.