This is a real mystery to me. Either:
1. OP is truly a sociopath/psychopath (not proven in any way) and somehow snapped - which would make sense if he were completely enraged. Thus, help, help, help was him mocking her (after all, we can't just shrug off her WA message to him about him making fun of her accent, nor can we just believe OP's testimony that he only did that one time over a conversation of him buying himself a house.)
2. No way in the world is #1 a possibility, so the help, help, help was a post release of rage and realization of what he'd done. It might have been a moment of madness for him, actually.
But I don't buy it that the help, help, help was delivered in the way OP claims it was in his version. If his intent was to receive immediate help, he would have done the very thing he claims he whispered-said-in-a-soft-tone-screamed-shouted at Reeva and called the police.
But he didn't call for help in the one way he would have most logically received it. Therefore, him yelling off the balcony help, help, help was not delivered in the logical and normal way in which anyone trying to get help after shooting someone they love would have delivered it.