Your Kobo sorts by what it believes to be the last name by default and this is done from the metadata and has nothing to do with the template. Also I have to wonder why you are including the series/series index in the file name since your Aura One will display series/series index without needing to so so.
My preferred Save template set in the KoboTouch driver configuration is:
Code:
Ebooks/{author_sort:sublist(0,1,&)}/{title} - {authors:sublist(0,1,&)}
The reasoning is to put all my books sent by calibre in a subdirectory and not in the root of the exposed storate ( Ebooks/ ) and then into subdirectories based on the first entry in the author sort ( {author_sort:sublist(0,1,&)}/ ) and finally a file name based on the title of the ebook - first entry in the authors list.
Since I can find any author in the full authors list using search, this keeps the length of the filename/directory path under control. Since the root directory has a maximum number of directory entries and using long filenames chews that number up surprisingly fast, a subdirectory is a quick and easy solution.