to add a condition on a meta value, you can modify the test like that :
function fq_disable_single_cpt_views() {
$queried_post_type = get_query_var('post_type');
$cpts_without_single_views = array( 'ait-item' );
$_ait_item_item_featured = get_post_meta(get_the_ID(), "_ait-item_item-featured", TRUE);
if ( is_single()
&& in_array( $queried_post_type, $cpts_without_single_views )
&& ("0" === $_ait_item_item_featured)
) {
wp_redirect( home_url( '/sorry' ), 301 );
exit;
}
}