Restrict level signups by email address or username

I use this code recipe to block certain email addresses from registering on my site. Originally, the code allowed only specific email addresses to join a membership level, but I modified it to block certain emails instead. Everything works well, but the issue is that the settings are created for each individual membership level. To block an email from joining my site, I have to add it to every membership level separately. Is there a way to make this code recipe use global settings? I want to add the email once in a global setting and have it restrict access to all membership levels on my website. Thank you.

/**
 * Restrict level signups by email address or username.
 *
 * title: Restrict level signups by email address or username.
 * layout: snippet
 * collection: checkout
 * category: registration-check
 *
 * This code snippet replaces the functionality from the Register Helper add on.
 * Make sure you are running PMPro 2.9+ and have the RH add on deactivated.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
//text area for emails and user names on edit level page
function my_add_restrict_by_email_or_username_settings() {
	$level = intval( $_REQUEST['edit'] );
	$restrict_emails = pmpro_getOption( 'level_' . $level . '_restrict_emails' );
	?>
	<h3 class="topborder">Restrict by Email</h3>
	<p>To restrict signups to specific email addresses, enter those email addresses below, one per line. If blank, signups will not be restricted.</p>
	<textarea rows="10" cols="80" name="restrict_emails" id="restrict_emails"><?php echo esc_textarea( $restrict_emails ); ?></textarea>
	<?php

	$restrict_usernames = pmpro_getOption( 'level_' . $level . '_restrict_usernames' );
	?>
	<h3 class="topborder">Restrict by Username</h3>
	<p>To restrict signups to specific users or usernames, enter those usernames below, one per line. If blank, signups will not be restricted.</p>
	<textarea rows="10" cols="80" name="restrict_usernames" id="restrict_usernames"><?php echo esc_textarea( $restrict_usernames ); ?></textarea>
	<?php
}
add_action( 'pmpro_membership_level_after_other_settings', 'my_add_restrict_by_email_or_username_settings' );

//update the emails and usernames on save
function my_update_restrict_by_email_or_username_settings($saveid) {
	$restrict_emails = sanitize_textarea_field( $_REQUEST['restrict_emails'] );
	pmpro_setOption( 'level_' . $saveid . '_restrict_emails', $restrict_emails );

	$restrict_emails = sanitize_textarea_field( $_REQUEST['restrict_usernames'] );
	pmpro_setOption( 'level_' . $saveid . '_restrict_usernames', $restrict_emails );
}
add_action( 'pmpro_save_membership_level', 'my_update_restrict_by_email_or_username_settings' );

//check emails when registering
function my_check_if_restricted_by_email_or_username( $okay ) {
	global $current_user;

	//only check if we're okay so far and there is an email to check
	if( $okay && ( ! empty($_REQUEST['bemail']) || ! empty( $current_user->user_email ) ) ) {
		//are we restricting emails for this level
		global $pmpro_level;
		$restrict_emails = pmpro_getOption( 'level_' . $pmpro_level->id . '_restrict_emails' );
		if( ! empty( $restrict_emails ) ) {
			$restrict_emails = strtolower( str_replace( array(";", ",", " "), "\n", $restrict_emails ) );
			if( ! empty( $current_user->user_email ) ) {
				$needle = strtolower($current_user->user_email);
			} else {
				$needle = strtolower($_REQUEST['bemail']);
			}				
			$haystack = explode( "\n", $restrict_emails );
			array_walk( $haystack, function( &$val ) { 
				$val = trim($val);
				return $val;
			});
			if( in_array( $needle, $haystack ) ) {
				global $pmpro_msg, $pmpro_msgt;
				$pmpro_msg = "Your account is blocked due to Terms & Conditions violation";
				$pmpro_msgt = "pmpro_error";
				$okay = false;

				//no further checks here
				return $okay;
			}
		}

		//are we restricting user names for this level
		$restrict_usernames = pmpro_getOption( 'level_' . $pmpro_level->id . '_restrict_usernames' );

		if( ! empty( $restrict_usernames ) ) {
			$restrict_usernames = strtolower( str_replace( array( ";", ",", " " ), "\n", $restrict_usernames ) );
			if( ! empty( $current_user->user_login ) ) {
				$needle = strtolower($current_user->user_login);
			} else {
				$needle = strtolower($_REQUEST['username']);
			}
			$haystack = explode( "\n", $restrict_usernames );
			array_walk( $haystack, function( &$val ) { 
				$val = trim($val);
				return $val;
			});
			if( in_array( $needle, $haystack ) ) {
				global $pmpro_msg, $pmpro_msgt;
				$pmpro_msg = "Your account is blocked due to Terms & Conditions violation";
				$pmpro_msgt = "pmpro_error";
				$okay = false;
			}
		}
	}

	return $okay;
}
add_filter( 'pmpro_registration_checks', 'my_check_if_restricted_by_email_or_username' );