Hi xberg,
Seeing the duplicate column error more than once sounds like that plugin installation is trying to run on every pageload. This could happen if your database isn't writable by the user, or if you have a database cache that's continually returning old data. If you check your database user's privileges, and also check for tables needing repair (using a tool like phpmyadmin), that may help.
If you still have trouble and need more details, please make a new post using the form at the bottom of the Wordfence forum here. (The wordpress.org forum rules ask us to keep each person's issues separate, and it also helps us keep track of open issues, so no one gets skipped in old / long posts.) Thanks!
-Matt R