If FDR knew about the attack on Pearl Harbor then is it not a calculated risk that the Japanese would not conduct a third wave incapacitating the base at Pearl Harbor for use in the Pacific Theatre?

Answer

But FDR did not know, that is a historical fact. Claims to the contrary are just lies. Michael Montagne
You need evidence to prove he did not know, or to disregard proof that he did know.
"FDR did not know." Is not a historical fact. It is not possible to determine whether he did or didn't, however you can use the weight of the evidence to suggest one way or another."  

Answer

Again, simply stating that "FDR did not know." without any evidence to support it is NOT A HISTORICAL FACT.
Roosevelt desperately wanted the US to enter the war, he states to William White, a close friend in 1939; "If Germany or Russia win the war or force a peace favourable to them, the situation of your civilization and mine is indeed in peril..."
However he needed the US publics backing. He spent a total of 12 years in office, completed revolutionary new ideas and introduced the first women ever to go to a presidential cabinet. He knew he needed the public support. A crisis like Pearl Harbour unites the nation in an act of revenge and war.
It is more likely however, that the information critically needed to know of the Japanese attack slipped through America's nets. With so much information around, much of it was intercepted. HOWEVER, it is probable that the information was cast out the system as it passed up the ranks, the most important information would go to the most important officer. Much information on Pearl Harbour was found in the 'pending' boxes of interception offices.
Finally, it is impossible to tell if Franklin D Roosevelt knew of the attacks. However we can use the weight of evidence to suggest one way or another.
I believe that America had the POTENTIAL to discover the Japanese attacks, however the poor system of sorting information led to the crucial pieces being discarded. Although a terrible tragedy, the Japanese attack on Pearl Harbour worked in Franklin D Roosevelt�s favour.

• You are asking Michael to prove a negative. If FDR had written "Japan will attack Pearl Harbor on December 7th", or credible witnesses had heard him say this, prior to the attack, that would prove that he DID know. No one has ever said that they informed him of the attack in advance or that he gave them any indication that it was coming. The total lack of evidence strongly suggests (but does not absolutely prove) he did NOT have any advance knowledge.