Are you familiar with the Sam & Max games/media? It might be a good reference for the tonal balance you're trying to strike; it's essentially a comic interpretation of crime and law (after all, they are the Freelance Police). Although weapons are featured as sort of characterization devices, the actual physical confrontations in the games are slapstick, and real world vices are mostly alluded to with innuendo and suggestion. The worldbuilding starts in a familiar grimy, jazzy, urban setting but the story scenarios are wacky and nonsensical fun.
My favorite humor in Lowball Hockshop is all about the comic mischief, like all the combinations of things Timmy gets in trouble with. This, juxtaposed with the affably menacing Family business and the sort of low-life but cultured environment.
I've found the mood indicators function very well as flavor enhancement, and I've developed a sort of different intuition as I've learned to read them. Like my initial expectations about their meanings were way off, but I seem to have learned to recognize some patterns that I can't articulate yet. The mystery is very fun, and I never want to find out how it works under the hood.
Narrative and subplots would be very cool! Keep chewing on these big picture ideas; I think you'll find something really compelling. I think it's wise to avoid realism about pawning, for the same reason you opted for simplified haggling. I'd personally love to see a bit more of the crime theme explored, comedically or otherwise.