I just published a v1.1 of the system, including (amongst other things) difficulty levels. You can still hack the system and make it work any way you like, but that should serve as a reasonable guide I think. There are more details about the update here: https://hlashbrooke.itch.io/roll-up-ttrpg-system/devlog/775251/v11-difficulty-levels-and-improved-balancing