I think he was either watching the mission unfold (either after dying earlier or by plan) or re-enacted it with the help of his crew. Probably a little of both.
With the second part … I am not sure any test pilots want to check that failure condition out, if possible. :- ) It could be just the Arma3 flight model being very forgiving but I can not think of a situation where loss of a rotor would have allowed a continuation of the flight. What I mean is I am not sure a situation would arise where loss of one rotor did not either destroy both (as far as I know, the rotors inter-mesh) or significantly destroy or damage some other part of the air frame.
Wouldn’t one of the cockpit instruments have gone haywire?