Except he wasn't in a place where 'armed home invasions that often ended in violence /death were not especially unusual'. He was in a high-security gated estate where home invasions weren't the norm at all. Not at all. And this was someone not really that bothered about security, as evidenced by sleeping with open balcony doors (as did many of his neighbours), not bothering to fix a broken downstairs window, and not being sure if his alarm was working or not. For someone who you think had a very real fear of a home invasion (despite the estate having had something like one minor incident in 5 years), why was he so lax about security? He was so petrified of intruders but yet relaxed enough to go to sleep with his balcony doors open.
When I lived briefly in a very rough part of London many moons ago (near a very famous prison) we were always worried about burglaries and violence and would never ever dream of sleeping with open windows, not unless we wanted our throats cut and our money stolen. When I moved to a leafy suburb years later, no one worried about that kind of thing at all. It was a completely different environment. OP's secured and monitored home was a totally different environment to the one where home invasions are a real threat. That's no doubt why he chose to live there, so he could feel safe enough to sleep with his windows open and not worry too much about fixing broken windows. His casual approach to security doesn't tally with the highly vulnerable disabled man in constant fear of intruders and violence. I think he felt quite safe at home.
In truth the ‘highly vulnerable disabled man in constant fear of intruders and violence’ only materialised after the murder when there was a desperate and indeed crude attempt by the defence to back fit him into this category. Unfortunately making up detailed stories then suddenly forgetting the names of the ‘witnesses’ somewhat gave the game away