I can't comment on uniforms and protocols for 1944 but I can comment on some of the howlers in the film regarding the handling of Lancasters. First I must state that my 750 hours on the Lanc were flown in the 1950's, after people stopped shooting at them.
Firstly, the Flight Engineer or Pilot didn't just stick a thumbs-up out of the window to request clearance from the ground-crew to start an engine, they indicated which engine by showing the requisite number of fingers.
Secondly, you would never start turning a heavily laden Lancaster as soon after take-off as they did in that film. You had to hold a steady course while you balanced acceleration against height gain as you retracted the undercarriage and got the flaps up and built up a climbing speed of 160 - 165 knots before reducing power from take-off to climb power. That took some time.
Thirdly, the German fighter tactics shown were those that they used against B17's in daylight and were quite unsuitable for night fighting.
I've just re-listened to a recording that my older brother made 25 years ago for a local school. He did a full tour as a Flight Engineer on Halifaxes and Lancasters with 432 Squadron RCAF at RAF Eastmoor and he describes a 700 aircraft attack on Karlsruhe in 1944 and makes the point that they didn't see another aircraft throughout the whole flight though they did run into severe slipstream turbulence over the target. The CGI views of a close formation of Lancs thundering through the dark skies over Germany was very impressive but totally wrong.