Getting into Jackenstein; The Frankenstein's monster inspiration would imply he's an amalgamation of something; based on the candle and pumpkin head, it seems he's supposed to represent a combination of a lightner (the candle) and a darkner (the jack o’ lantern overshadowing or literally ‘darkening’ it). In addition to that, ‘Frankenstein’ was the doctor's name, not the monster, implying that despite the apparent inspiration he takes from the monster, he's both. Combine that with the point before that, and I'm to assume that (based on the classic head bolts denoting him as such) the darkner / pumpkin is the monster, and the lightner / candle inside is the doctor / Frankenstein.
Continuing onward, just as Frankenstein was (itself sub-titled ‘The Modern Prometheus’), Jackenstein also seems to take inspiration from Prometheus - and, given the repeated intermingling of the two during his appearance, equates the light to fire, in Prometheus’ context of it as a symbol of forbidden knowledge. Jack consistently phrases ‘light’ as ‘laight’ - with the root ‘"ai-" meaning "to burn", later supported as the intended meaning when he shouts ‘NO!!! NOT THE LAIGHT!!! IT BURNS!!!’ (which, unrelatedly, also invokes his halloween theme by referencing vampires, lol) during the UNLEASH act, and his check dialogue, ‘An unsightly beast that lives in total darkness.’, which vaguely translates to ‘an unseeing beast that lives in destructive ignorance’ and correlates darkness to a lack of ‘sight’ / an inability to see (in the sense of ‘seeing’ as "perceive mentally, understand”) and ignorance, in contrast to light, which enables sight / knowledge of things.
Speaking of which, as soon as the lights come back on, Jack says ‘DOAN’T LOOK’ and then covers his own eyes, as though he's telling himself not to look. The implication here is that his ignorance / life ‘in the dark’ is self-imposed.
Anyway, going back to Prometheus, Jack’s intro speech to the dark zone, “... LAIGHT... ... WHO DAIRE BRING LAIGHT HEAR... ... GO... BACK…” reads in full as “[those] who dare bring light hear “go back”” - which, still reading light as fire, references Prometheus’ act of bringing fire to mankind. The “go back” (i.e. return to a time before such), however, implies that in this case said forbidden knowledge is deeply unwanted, and that there's a desire to return to a time before it was brought. Take that motif into the context of Jack himself, and it would seem to imply that his self-imposed ignorance / rejection of light is done out of a desire to go back to a time before he was given fire (because he's a candle haha) / became knowing.