1: Yes
2: No clue, so none.
3: AV-8B, c'mon VTOL is just plain cool!
4: Difficult question, the Harrier certainly brings some unique functionality but will mission designers utilise its VTOL capability to have it stationed closer to the front? I remember seeing old reports from Cold War exercises where that was the main strength of the platform, basicly operating from gras fields few miles behind the front line. TL;DR VTOL should be sufficent to make it utilitarian.
5: Not sure what you mean with this one., are you referring to the AV-8B+?