Conditional based on post meta

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;
    }

}