Some questions which make it harder to make a theory as to how things happened cause I have hesitations to accept the below as fact.
1- Toilet door key : OP's version depends on the key being inside and the door locked. However ;
* The key chain at least had another key on it (possib.bedroom door key )and that is very unusual for an inside door to have keys altogether like that. why would another room's key be on the toilet door ? The green thingy rather makes it look like a spare set for the main bedroom.
* How did the key fall on the floor with the bat's hits? That lock mechanism should be turned right or left for unlock position for the key to fall down.
On the photos the key is on outside of the toilet door .Me thinks that could be the initial position and OP had to add that key found on the floor thing because if it hadn't fallen on the floor , OP wouldn't need to put it the other side where it is found but rather reach out his hand and turn the key to right or left.
That's why the affi explained this key found on the floor thing with detail which makes me suspect abt its truth.. (My interpretation )
* OP had the gun ready in hand with bullets .. he had previously shot thru the door.. Why not try to unlock the door with shotting at the lock part first instead of beating the door with the bat.
* Door panels rather looks to me taken out partially by hand ..not big crashes for the key to jump on the floor..
So, at some point that night OP might have locked her inside. Quite possibily between the two set of shots heard by Stipps imo. maybe to silence her hiding behind the door ...
Pure speculation and could be wrong
I've long thought that might well have been what happened and have never taken it at face value that Reeva locked herself in, as we have only ever had OP's word for that .. plus also those things you mention about that type of key just falling out of the door like that, I don't think that a key turned in a lock would come out that easily, if at all .. in fact I would much rather have seen them set up an experiment for that, rather than that 'gunshot v bat' sounds thing. I want to know exactly whether that key could've fallen onto the floor .. I don't personally think it could .. but then again, why would OP make up quite such an elaborate story about that when he could just as easily have said he put his hand in to reach round and take the key out of the lock? <<-- that is my only doubt about him having locked her in there. Then again, if he had picked that key up off the floor, then I'm sure it would've had blood smears all over it, yet it looks pretty clean to me in the photos.
I'm wondering if the woman calling 'help, help, help' was when he was dragging her to the toilet to lock her in? .. and he was mocking her with his 'help, help, help'? I'm not sure if that fits the timescale though ..