is it dumb to save resources and beat something in spite of difficulty
But you're not saving resources on that, on the contrary, you're constantly losing sanity - which is, arguably, far more important than kerosene. Although YMMV, of course.
is it dumb to figure out a way to beat something you shouldnt be able to beat
In-setting (diegetically) - most certainly. It's not a high fantasy game where you're playing an adventure seeker and expect to be rewarded for bravery. In a horror-ish setting, bravery is punished - which is what we have here.
is it dumb to expect a clearly visible box to require a lanturn to loot
If the game was telegraphing so hard that you were doing something wrong, and you persisted in doing it...