local host is your local network and root means given high or special access, which similar to the admin account on your Mac but, with more privileges.
More than likely, what you are seeing is nothing more than the network access that your ex used to administer the home network. What you stated in and of itself is nothing to be alarmed about. If you are concerned about your ex gaining access to your Mac, go to system preferences, and make sure remote login and remote access are turned off. And if you are still concerned, change the admin password on your Mac as well as your internet router.