I don't buy the whole aileron induced stall-flick. It's going to take an almighty pull and a lot of G to get close to the stall flat out, clipped wings or not. Running figures conservatively, a 130mph Vs would give at least 14G to get a stall at 500mph - you don't accidentally pull 14G because you got a bit excited rounding a pylon! Alternatively, at 5G, the stall would be a smidge under 300mph. To put it another way, if the clipped wings were going to put it that close to a stall they wouldn't be clipped. Flying around on the back of the drag curve isn't fast.
The video really isn't that clear, half the artefacts could be down to the camera.
The underside of the wing will see pretty much the same pressure even if you stall - the separation of airflow is from the top surface. No reason for the bottom skin to 'balloon'. I don't see any nose drop either, I see the aircraft react to the lift vector being turned further round towards the ground. No real visible yaw either, and any yaw generated by an asymmetric stall will tend to perpetuate the condition, not recover it. Nor do I see the torsion, but flicks do exert a tremendous load on the tail feathers.
I also think it's a little presumptuous to claim the roll rate is higher than standard, it may or may not be: the clipped wing will aid roll, but the ailerons are tiny compared to the original where they go to the end of the wing - so there's 10 foot less aileron too.
Trim was most likely nose down (the earlier posted photo from another flight supports that), or at least we can say that at high speed the a/c would have required a significant nose down input.
WRT the Oil Canning: Assuming the photo is from the same flight, it is significantly before the incident - because it is on the right side (which is pointed to the sky mid turn), and the tailwheel is stowed. Interesting, but I don't know what it means, if anything.
I don't really want to make guesses, but my money's on a trim failure precipitating the wobble. The pick up of the left wing was probably completely instinctive, whatever caused it, and probably the last deliberate action in the aeroplane.