Yeah, I finished the last night with one preserver left. I think the thing with Flash is that the cooldown may actually be more of a balancing factor than the oil. It makes less sense in the fiction unfortunately but something like upgrading the Flash cooldown rather than the total oil supply might be a bit smoother in terms of whether the upgrades matter or not and how the player manages usage. But I'm not sure I like the incentive there - to use Flash as early as you can get away with basically, so that it has refreshed by the time you need it.
The story I'd say was atmospheric mostly - sort of part of the overall aesthetic rather than necessarily 'I'm playing in order to reveal the next letter'. At atmosphere I like it, I think that's what this particular kind of writing style is better for than e.g. sequences of events or twists and turns.