1. Yeah sure, worst case TR control malfunction with the TR servo going full extension/retraction would likely not result in the high yaw rate seen on the CCTV.
4. Yeah sure, no NR and she falls out of the sky. But if you've hauled in full collective and sucked the NR out of the system (NR might go as low as 70% with both engines at topping??) the MR is still providing lift, and the TR is still providing some thrust, and you shouldn't get that high rate vertical descent, nor that very high yaw rate seen in the CCTV.
5. Yeah, I reckon....the power has been reduced evidenced by the initial high yaw rate reducing as it descends (the vertical fin is having more influence against the reduced engine TQ).
6. When you suddenly lose TR thrust the nose pitches down. The tail doesn't need to fall off for the nose to pitch down. This is the part many pilots have difficulty with in practicing this malfunction (The logic in my conclusion is I've done it hundreds of times). The instinctive reaction is for the pilot to lower collective and apply aft cyclic to counter the pitch down. This causes the NR to go off the scale, and I'm talking 130%+.