I definitely HC him as queer. I always kinda shipped him with Radford, though I also super love your idea of him having the most normal husband who is completely oblivious to the weirdness and the Mayor being Generally Evil, lol.

in his youth he was the mirror darkly version of Marshall.
I absolutely fucking love this idea, oh my god! Now I want like. Pre-series Mayor Chisel fic about this!!

I do kind of like thinking of him as an Eldritch Horror, but I think him being a Human evil makes way more sense.

Okay I never actually gave a ton of thought to the "going from bank manager to mayor" beyond "they needed a body and had an actor who could do it" but it being the weirdness/a monkeys paw makes way, way more sense.

I...Don't remember the Chisel as Harley's dad discussion but damn does that intrigue me!!