So I'm writing a screenplay...

[Bengalzona]

I like it because I'm into the dark comedy and period piece genres.

In style, it reminds me of "Fargo". And that is not a bad thing. You'll want characters with particular flaws and ticks: the stutterer, the hypochondriac, the mumbling farmer, the used-car salesman with a Herb Tarlek suit, the Farrah Fawcett hair woman etc. But I think one of the keys in this type of comedy (and I suspect you'll probably agree) is to keep the the people as deadpan serious as possible. It's their world and they don't necessarily see it as funny in the same way we as outsiders do. The humor is in the surrealistic situations they get into

Perhaps you could have one somewhat-normal townsperson voice-over an introduction and narrate portions ("Elmer fed his hogs everyday. And he would again today."... as they feed his body to the pigs). Not really necessary, but it can be helpful at times.

I don't think you ever need to delve into the money and where it came from. That can be a MacGuffin.