1) You could, the evidence we get is all we get to go off of. While it may look like RDM, it may have been a simple mistake. Usually players contact that player and apologize and comp them for lost gear or inventory.
2) If you showed that it was an accident, your ban would be lifted. Tough to penalize a player for an accidental kill (wrong place, wrong time).
3) This one is such a grey area, but just look at the rules:
RDM is killing another player without any type of HOSTILE role-play being initiated and reasonable amount of time for the target to react.
Intentions must be clearly stated to the intended target, and they MUST be given reasonable time to react.
While you did give the player Hostile intent that his life was in danger-> He is able to fire upon you
Reasonable amount of time to react -> Well he was able to get out and find cover, so sufficient amount of time is given
Intentions -> What intentions were said or texted? Appears to be none in this scenario. One could argue and compare it to warning shots given to helicopters, however, you disabled the vehicle.
So in conclusion, you would still need to initiate with your intentions.