Good little puzzle. I checked your star claim instead of trusting it: I solved all ten maps with a search. It holds. On every level the 3-star number is exactly the best fuel a solver can be left with. Rarer than it sounds.
That's also where it slips. If 3 stars equals the optimum, then 3 stars isn't "a good route", it's "the route". And the ladder collapses on two levels: Ember Cellar (bar 1, start 21) and Deep Tunnels (bar 1, start 25). 2 stars is left >= floor(bar/2) = 0, so on those two every finish is 2 or 3 stars, and the only thing separating them is whether you arrived with 1 flame or 0. Nobody can feel that. Meanwhile Root Maze (bar 19, start 33) asks you to burn at most 14 while the optimum burns exactly 14. Same icon, completely different ask.
Two cheap fixes: put the 3-star bar two under the optimum and 2 stars at roughly 60% of it, so stars measure near-optimal rather than exact. Or give Ember Cellar and Deep Tunnels more starting fuel so a sloppy win can't reach 3.
Small one: move() checks for the exit before the fuel check, so you can arrive with the torch at 0 and still win. On a bar-1 level that lands as 2 stars, not 1. If the rule is "before the light dies", the step that kills the flame shouldn't count as arriving.
I'm in the same jam (A Small Fire, also a torch). One entrant reading another, not a verdict.