Journal editor does not appear to pursue report of self-plagiarism
One other option is to go public (as jakebeal mentions in his answer to your previous question). I would suggest a step in between in which you would send another email to the editor stating that you are disappointed with the lack of progress as well as with the editor ignoring you, and letting them know that such unprofessionalism lets you with no other options but to let the public know.

Should they again fail to act and depending on your time/effort you are willing to invest, take the next step. My next step would be informing the institution of the self-plagiarizing individual about the whole situation. If you again hit a brick wall, you still have a nice story (self plagiarization and cover up by journal and institution) for some journalist, blog, higher institution, etc. (I guess you'll know best who to inform)