The DC-9 incident referred to,did in fact take place.However,it wasn't discovered before the QAR (Quick Access Recorder) was examined!
The Captain was on his very last flight before retirement,coming from STO to CPH,so couldn't be fired,the co-pilot was grounded for some short time and then returned to service.
It happened close to SVD VOR in SW Sweden.
As for the Dash 80 barrel roll,it was performed over Lake Washington on National Boat Race day,an annual Seattle event,and an amateur film shows the plane to be doing a barrel roll,definitely not a chandelle!Also,as mentioned,there is the famous shot from the cabin of the plane being upside down.
Properly flown,the barrel roll will feel just like any other unaccellerated flight.British master pilot Neill Williams described in one of his books how he barrell rolled a Canberra jet bomber without his navigator realizing it.
"Luck and superstition wins all the time"!