Aight, let's see...
1. Engine is plotting something and playing his own game. No strolls, no nothing, I don't believe him. Maybe he was looking for some artifacts, like items with strong emotional connection of their past owners? Maybe he's looking for somebody out there, some kind of foe, renegade etc? Maybe he's looking for info? He keeps saying how valuable info is in this world after all. Would've made sense.
2. Alright, so aberrant beasts become the same types of monsters and create some kind of ecosystem. You know, what I think? Since it's a surface, maybe it's not only about emotions connected to the trash falling from the Skypeople. What if whatever base instincts animals had ALSO affects items and matter of this world? This is clearly a post-apo. Maybe soul-bound items and animals dying of radiation, pollution and hunger kinda mixed together? Man-made emotions + animalistic instincts create entities akin to all those animals of the past?
3. 15 minutes will be very important at some point. I can already see something like leaving somebody alone in contamination zone, while taking away their breathing mask. As a punishment or out of cruelty, maybe by some kind of antagonist group. ALSO I imagine we might in the future see somebody with insane lung capacity, surviving without mask for hours due to long intervals of not breathing <3