First, I don't think the Japanese are going to strike before the oil embargo, so something like this could only happen a few months earlier than the OTL attacks. Really, I can't think of any good reason why omitting the strikes on Pearl Harbor and the Philippines advances things.
Second, this really was the best Japanese strategic option, or second best after just folding in the face of the embargo.
Striking against the USSR doesn't get them the oil and chances of success are iffy at best.
Its better to wait for the US to come into the war than trying to eliminate them as a factor from the outset. First, you really can't eliminate the US as a factor with one surprise attack. Its a continental country that is the world's largest economy. If they lose the Pacific fleet they can always move in naval assets from the Atlantic. They can eventually replace the ships.
Second, having the US come to you fits better with the overall strategic concept of taking alot of territory, and defending it until the US and UK decide its just better to make a deal and concentrate on the war in Europe. That's alot harder to do if you open up with a direct act of aggression on the US. Make FDR have to convince Congress that the US has to come in to save the British empire.
Third, though people probably didn't grasp this, the Japanese advantage in carrier aviation in 1941-2 was big enough that they probably would have won a naval battle in the open ocean against a USN attempt at relieving the Philippines. The attack on Pearl Harbor was fairly risky and could have gone very wrong. Tactically, again it was better to make the Americans come across the Pacific to fight.
Fourth, the "reserve" people talk about being needed in case the US came in could have been the forces historically allocated to Pearl Harbor and the Philippines, which by definition were not used against Java and Singapore. They also only allocated ten of the fifty or so army divisions for the strike south, and this includes the Philippines campaign. There would have been enough for a reserve.
Without Pearl Harbor, in practice I suspect they could have taken Malaya, Borneo, Java, and Sumatra much the same way as the Japanese occupied Indochina. Burma would have been nice to cut the main supply route to the Chinese nationalists, but could have been left for later, and in the mean time you can use forces based in the nearby islands to make Rangoon unusable as a port.
In terms of what would have happened, I think FDR would have asked for and gotten a declaration of war on Germany, Italy, and Japan after the fall of Singapore and Tobruk, to rescue the British. This would have echoed what Wilson and Congress did in 1917. But it would have been very controversial, and it would have given the Japanese the chance to ambush anything on the way to reinforce the Philippines. And they already would have taken what they needed in the east Indies.