I mostly agree, but the key factor was getting on planes with mostly empty seats and lots of fuel. Try to get a flight after 7:30 AM with empty seats out of a major Eastern city.. IOW I think they would have been happy to board an empty flight to the West Coast at 12:00 PM if one had existed.

Dive bombing the towers would probably have immediately brought the towers down, due to failure of floor trusses over many floors. I don't think causing the towers to fail was even in their plans - it was for them a happy accident of the Towers' unique structure.