Okay, I deleted this harmful plugin from all our sites from the dashboard.
The one where I was locked out I deleted manually.
You can do this by using your ftp program. The folder is located in /wp-content/plugins/
Just deleting it worked for me.
Honestly, I have not been that angry for months. Now I can set up a new security plugin and I am already late for dinner.
Thanks again, iThemes!
