I have 4875Kg as a memory for the Mk 7 (also in the 90s).
Interesting that the RN allowed the display manoeuvres because the AAC ones had G meters fitted, all the manoeuvres were flown on a fully instrumented aircraft at Westlands and there were large fatigue/servicing penalties for each display manoeuvre.
I flew the 90/90 roll a few times without 'jackstall' and all the displays were done with pitch and roll AP lanes out (since the gyros would topple anyway) but retaining yaw channel. There was also a 140Kt IAS limit as it was the VL for the TOW booms.
I still don't believe RBS or jackstall are possible in that aircraft - the back flip hover to hover from 1000' to 700' was a 3 G manoeuvre no matter how carefully it was flown and it was good as gold.
I don't know of any AAC Lynx display pilot who has been 'flicked out' of a manoeuvre although the Eagle Roll was a tricky one to get right.
Unusual to have a problem in a vertical dive, even with a rapid roll, but the speed does increase very quickly in that configuration, especially without the drag of the TOW booms.
A rapid right roll at high IAS would give the advancing blade a much higher AoA than normal, perhaps it was high-speed stall that caused the problem.