You underestimate the isolationist frame of mind that the US had. It's why many countries consider the start of WW2 to be the invasion of Poland, while the US considers the start of WW2 to be December 7th, 1941. Until then, it was "Europe's War."
Unlikely. I've never seen anything that indicated that Hitler's Lebensraum involved the United States. He was content with ignoring the United Kingdom. He held his forces back to allow the evacuation of Dunkirk happen, in a show of good faith to the British, in hopes that he could agree to peace with them. He knew that the possibility of conquering the British Isle was virtually impossible, which is why they dropped Operation Sealion and tried to take the UK out of the war indirectly....primarily through the Battle of the Atlantic, as well as an attempt to bomb them into submission with the Battle of Britain.
Also not necessarily true. Many of the ships destined for the Pacific Fleet (i.e. the new Carriers and Battleships) were just recently commissioned and still in the Atlantic and the Carribean, and hadn't gone through the Panama Canal yet. Even if he did know of the attack, it doesn't mean he could have done anything to stop the inevitability of it.
Evacuating all of the ships would have compromised any intelligence advantage the US might have had, as it would be an indicator to Japan that their communications were intercepted. It would have also caused more important targets (like the giant Fuel Depot nearby that was absolutely essential to any naval and air operations in the Pacific, and arguably way, way, WAY more important than any of the ships in the harbour. Losing ANY of the aircraft carriers would have severely compromised the effectiveness of the Pacific Fleet, much worse than the loss of obsolete battleships and picket ships.
War is a dirty business, and lives are sacrificed. Operations that have zero chance of success are planned in an attempt to feint the opponent and help ensure strategic success. For instance, the Soviets sent their men to be slaughtered in the Battle of Kursk. In doing so the Germans achieved an operational victory, while at the same time pretty much ensured total strategic defeat.