I was looking in the workshop for tweaks and QOL mods to improve the quality of my server and i found something really interesting. It seem that someone made something similar to you but axed on an XP multiplier of any skills. Something call "Ultimate xp Tweaker" i dont know if it can help you to understand more of how it work in the lua and how he add it in the Sandbox options. But i was thinking maybe it might be useful to you. Regards