First of all…

Your action is called rguroo_email_verification_form, so you should use it when registering your hooks. But you use this instead:

add_action( 'admin_post_nopriv_email_verification_form', 'verify_and_sanitize_email_form', $priority = 10, $accepted_args = 1 );
add_action( 'admin_post_email_verification_form', 'verify_and_sanitize_email_form', $priority = 10, $accepted_args = 1 );

It should be:

add_action( 'admin_post_nopriv_rguroo_email_verification_form', 'verify_and_sanitize_email_form', $priority = 10, $accepted_args = 1 );
add_action( 'admin_post_rguroo_email_verification_form', 'verify_and_sanitize_email_form', $priority = 10, $accepted_args = 1 );

Also… These actions don’t take any params, but you declare they should take one param (but later on, your function doesn’t take any…)