The dispersant is essentially glorified detergent and biodegrades over a matter of weeks. No more chance of it becoming gaseous than the box of detergent in your laundry room.
As for a hurricane, they have little effect deeper than a few hundred feet. It would probably help biodegrade the oil nearer the surface by oxygenating the water.
Um no, corexit 9500 is not essentially a glorified detergent.
I stopped reading right there.