I think this game sounds amazing! The core train management system sounds engaging, and I think you're on just the right track with that comparison to FNAF. I'm also getting some 'Papers, Please' vibes, if you've ever played or heard of that game (it's a masterclass in that "getting into the groove" feeling), which is absolutely a good thing. One thing I would say, though, is that your scope sounds absolutely massive- most game jam games are roughly 5 minutes long, and you're prepping to create a game that's, at minimum, 15x longer than that (5 levels 15 minutes long = one hour and fifteen minutes of content), with all kinds of different levels and imaginative demons and unique puzzle solutions, and while that full game sounds amazing, it sounds like a lot of work to get done in only three weeks. I'd encourage you to make a single level with only one or two of your favorite demons, and if you've still got time you can expand from there. Either way, I'm very excited to see where this game goes, you've got a wonderful idea and I'm hyped to see you execute on it.