When you edit the author and title in Wndows MobiPocket Reader, all it does is add the information to the .mbp file, not the original .mobi file, and this gets lost when you transfer the ebook to the Gen3. The --mbpfile option to mobi2mobi will copy this information into the .mobi, or you can add it using the other mobi2mobi options.
I suggest testing the result first using Windows MobiPocket Reader, by deleting the .mbp file and seeing if the new author/title is picked up as expected from the .mobi file.
I don't know what the Gen3 uses as the title, but on the Kindle there have been reports that the "updatedtitle" will over-ride the longtitle (from --title), and that if this already exists you may need:
Code:
mobi2mobi --outfile [output filename] --exthtype updatedtitle --exthdata "[Corrected Title]" [original AZW/MOBI filename]
See
Change book title to remove typos and extraneous info?.