That is an absolute honor to hear. Thank you!
Yes! Exactly. It is based off true human traits more than any would want to admit, and it's exactly that kind of apathy and the desire to just keep on going on into another day without actually fighting to save ourselves from imminent threat/death. We worry instead of taking action too much, and very often end up in our very own loopholes of nothing but anxiety.
Though given the first two victims were killed while asleep, and third on the toilet, it could still be a woman, given how fatigued they all must've been due to insomnia/nightmares. It could also be that it wasn't only one killer. In a reply to another comment, I touched the idea of how a person could kill another because they were convinced they were the killer, and were just tired of how ineffective pointing fingers was. Worst that could happen was another person dead, the death of which attributed to this mysterious killer, and the best that could happen... well, they'd kill the killer. :P
The narrator is indeed a great suspect. Though he struggles, he also has enough strength still to lift the upper (heavier) half of a human body and carry it. And exactly as you pointed out, whereas others were staring into nothingness, or forcing themselves to eat to not starve, he is casually playing with a ball, suggesting he has energy to spare, however scarce.
Great observation!
Thank you for reading! :D