So. It broken.

Added some screenshots of how it looks when I run it from the Godot editor so you guys can see what it's SUPPOSED to look like.

Godot appears to be struggling with loading certain image files, as if they weren't included in the project export (eg: no loader found for resource: res://dialogues/portraits/wizard_vendor.png) but this can't be the case because the exporter is set to "export all resources in the project".

If anyone has any insight about this I'd really appreciate it - I thought it might d be one of those issues where a night of sleep would make a quick-fix come to me, but I'm still hitting my head against a wall 15 hours later.