Remove personal data without doing a full reinstallation
Create a new user with admin privileges named Victor (or any name of your choice)
Login with Victor, and remove fully (Delete the home folder option) all other accounts.
Start Disk Utility and select the Erase function (what you did in step 4).

Just do an Erase Free Space and place the cursor in the middle position which will do a 3-pass erase. This is sufficient to protect you against any normal user and normal recovery software.