I had few spare minutes so I went ahead and tested everything.
Changed the $table_prefix = 'test_';
variable in wp-config.php and installed a new WordPress site.
All DB tables were created with table prefix test_.
Installed WooCommerce Email Verification.
Your flat DB table was created successfully wev_temp_user InnoDB latin1_swedish_ci.
I had to modify some of your code for testing since I do not have woocommerce and your plugin is hooking into the woocommerce global global $woocommerce;
obviously.
Your plugin functions without any problems or issues.
So I stand corrected that you would need to add $wbdb->prefix
to any of your code since I misinterpreted what your plugin code was attempting to do.
Installed Better wp security and used the DB table prefix renamer.
Your plugin no longer works. So the problem is some conflict with better wp security and your plugin. What that is exactly I am not sure. This test was performed to find the source origin of the problem and not to go any deeper and provide a working solution.
I will notify KushClean that what caused the problem is better wp security and not your plugin. I will also ask him to reverse his star rating/vote since your plugin is ok and the problem is being caused by the better wp security plugin. Thanks.