Did Hughes' airplanes, such as the H-1 Spruce goose and the XF-11 have significant contribution to aviation history? How about the Senate hearings Howard Hughes was called upon to answer on the taxpayer money he used to construct the H-1? Also, Owen Brewster made these hearings a big deal as he wanted to defame/ruin/sack Hughes Aircraft, as he was close with Juan Trippe, the CEO of Pan Am; Hughes biggest competitor. How different would modern aviation be if Owen Brewster won the Senate hearings and furthermore Pan Am acquired legal monopoly rights for international air travel?
Howard Hughes basically set the stone for building planes bigger and faster for civilians, before him, it was all military advancements and none of it could be useful to the public except radar. He helped show other plane builders figure out how to get around problem such as the smooth rivets on one of his earlier planes. I really don't know much about the other questions though.