Well it's fine that you have your skill/item entries in itemdata.txt and not skilldata.txt, it doesn't really matter that much. The items (the skillbooks for the skills) don't need descriptions, but they do need display names, but that should be part of the root template and shouldn't require a translated string key thing I don't think. Just make the root template, point the entries to the right stuff and it should be fine. I'm not sure if you're having issues with editing the root templates you've made or you have to create new ones if you have to change them, but that's an issue I've had.
I also don't think you really have to make new entries in the object data for the skillbooks; you can just point the root templates to a skillbook stat entry with whatever level requirement you want since that's basically all the information that's in those entries.
