I think it will be a lot easier to just wipe the directory clean and start over
No you should definitely NOT do that.
Rename this plugin's folder as suggested earlier and then see if you can at least log back into your site.
If you activated some firewall features and you can't find the .htaccess file, then ask your host provider to help you.
is the plugin of any real benefit to preventing hackers from accessing my domain
Yes it is - the plugin serves a useful purpose from the wordpress perspective and in terms of protecting access to your wordpress site amongst other things.
There are other doors (not related to wordpress) which a hacker can utilise to get into your site not just wordpress.
Therefore your question cannot be answered easily because it depends on many factors ranging from your host's server security through to your individual wordpress setup.