regardless of whether Hull was a Soviet agent, whatever he wrote must be approved by FDR first before it was presented to the Japanese. that alone shows that FDR didn't have the domestic backing to start a war if Japan didn't fire the first shot.
anyway, its all what-if history. fun to think about, but ultimately there is no right answer.
No, it showed FDR was not the rash type who squanders domestic political capital to execute foreign policy moves now when he could accomplish the same thing for less expenditure of political capital by being patient and methodically preparing the ground, both domestically and abroad. He knew the United States was overwhelmingly powerful economically, industrially, and demographically, and getting into the war a little sooner or a little later would not change the fact that the side America was on would be the eventual winning side.
Roosevelt was a very shrewd political operator. He realized the fewer political capital he uses to get the US into the war, the more political capital he would retain to influence the conduct of the war and the manner of its end, and shape the postwar world. In the end, maximum influence on how the war would be conducted and what kind of peace would emerge from the war was far more important than whether the US entered the war in May 1941, dec 1941, or August 1942.
Hotheads wants to get into war now, and simply have faith victory will come, at which time things can be twisted by brute strength to be better. More cunning operators think through how to enter and conduct the war in order to have the maximum leverage at its conclusion.
In the end, Roosevelt was already doing a fine job husbanding his political capital for the conduct and conclusion of the war, then the Kito Butai and Nagumo came along to give him an unexpected and massive additional windfall of political capital. His patience paid off even better than Roosevelt could possibly have hoped.