You may have deleted the app in applications but you didn't delete those launchagents. So delete them and reboot.
Also those launchagents refer to some other sony software as well. That software won't matter once the agents are deleted other than taking up a bit of disk space. But if your a purist search your system for "sony". Either use the finder's find command (command-F) and search by kind filename. Or use a better search tool like Find any File. Hopefully those additional files will have "sony" in their names. Like I said don't worry if you can't find the stuff.
I don't use my eReader very often and so a while back I figured out how to do this and today I had forgotten how!! So here's to help you and I and every other dummy who keeps forgetting!
Sony eReader with Mac:
How to put ebooks on reader when Error appears
1. First you buy your ebook(s) and download it to your Reader Library.
2. It goes to Status then into your Library.
3. Now go to Finder your book should be in the recent/Today section in epub form.
4. Open another Finder by going to File and New Finder Window.
5. In the new Window open Reader under devices.
6. Continue opening database/media/books.
7. Finally take the new ebook from the first Window and put it in the second Window.
8. DONE! And ENJOY!!