Ah I thought I had remembered there being a version of it on rest.
Annoyingly on-rest scripts are located in an ".assets" or sometimes a "level" file. Unless they have a referenced to a globalscript/globalexpression it's not something that Apotheosis is capable of editing. And as far as my experience goes, even with a tool like UABE that can open assetbundles, such files seem prone to corrupting or are very finicky to make alterations to.
Removing the script setting "b_Xoti_Nightmare" from the Gaun statue conversation would have been my next suggestion. Really my only hesitation in suggesting it first, would be that doing so makes it so that once that conversation has played the next step in Xoti's quest becomes reliant on the mod to progress.
All things considered though, it's the best solution. I would suggest moving your script for Magran's teeth completion to a mod scripthook instead. That way you'll avoid the possibility of conflicts arising from other mods that make changes to Xoti's hub.
Great idea for a mod by the way! The pacing of Xoti's quest has always struck me as pretty bizarre.