Cannot access Admin after deactivating plugin

I’m not sure why you need to deactivate in the first place, was it not working?

I think you don’t understand how it works, which is perfectly ok. But not understanding how it works doesn’t mean that the plugin is forcing you to do anything. If you delete the plugin, then it’s not having any effect on your site => therefore not causing a problem in and of itself.

This plugin is 1 part of a larger solution, outlined here:
https://www.icontrolwp.com/blog/enabling-cloudflares-universal-flexible-ssl-wordpress-without-infinite-redirect-loops/

So follow the guide there, but do it in reverse and you should be able to get your site back to non-ssl. When I say do it in reverse you must undo each setting but starting from the last step and working backwards.