I used to live in a crime ridden part of Africa. NOt SA (although we stayed there too, so am familiar), but crime levels similar. We were a 'targettable' family, and I am well aware of procedures, guards, hijackings, and how hideous break in and home invasions can be.
THere is so much about that evening that doesn't make sense. I understand the perpetual fear, having to question every movement, every sound. I lived it too. I know how it feels to be in a situation where, if it is an intruder, you are going to have to kill them before they kill you.
having said that, I cannot understand (bearing in mind this constant fear - pervasive, there is never a moment when you are not thinking about it on some level - crossing a road, getting in your car, going upstairs/downstairs, or even out into your own (guarded) garden) the following:
lights not working, if they were necessary ones (it is almost unheard of for wealthy people to not have staff, so not just a question of not having time/not being able to reach)
no outside security lights
leaving ladders around (OP says this is one reason why he was so edgy - why not have them moved?)
going to sleep with the balcony doors open - this just would not happen in the home of anyone who was as on edge and alert to potential intruders as OP says he always was.
getting up, hearing a noise, and NOT alerting the person next to you that you think there is an intruder. just muttering something is not the way to do it - you need a cohesive response (and everyone knows this), as otherwise you are leaving them wide open to abuse and assault (if you are overcome instead of overcoming the intruder, then your partner/children/whoever you have not roused sufficiently are just sitting ducks, tbh). OP and Reeva both grew up in SA, they would know that intruders are a possibility - it is not as though either were a stranger to this background environment. I cannot fathom why he would not ensure she was aware of the situation fully before going through all that he did. No response from her should have given him pause for thought.
not having a panic button/not triggering it even if you are going to tackle yourself (this will depend on the state of the guard response - some companies better than others, but again, money not the issue it would appear, and there are always good companies as well as the corrupt/inefficient ones) - much as the response might be 'shoot first ask questions later', the other ingrained response is 'alert people to help you first, explain later if necessary'
I, too, know too many people who have been robbed, assaulted, raped and killed. I know this stuff happens. And I still cannot reconcile it with someone getting up in the night, and doing their own thing with no thought for their partner, putting both their lives at risk (if it hadn't been Reeva in the toilet, then she would have been at risk - OP had no way of knowing whether there was one intruder, or more, or whether they had stayed contained in the toilet or crept out (given how absolutely pitch black it was 
) in between some of his toing and froing gathering fans, fetching his gun, etc. It just doesn't make sense.