few small problems

1. I miss pageposttypes for some page types and for terms as single string so that i could use it in GA. This solves it for me:

add_filter ( 'gtm4wp_compile_datalayer', 'centropol_gtm4wp_compile_datalayer' );
function centropol_gtm4wp_compile_datalayer($datalayer) {
    if (!array_key_exists('pagePostType2', $datalayer)) {
      if ( is_404() ) {
          $datalayer['pagePostType'] = 'error_404';
          $datalayer['pagePostType2'] = 'error';
      }                                                     
      if ( is_search() ) {
          $datalayer['pagePostType'] = 'search';
          $datalayer['pagePostType2'] = 'search-'.get_query_var('paged');
      }    
      if (is_archive()) $datalayer['pagePostType2'] = 'archive-'.$datalayer['pagePostType'];       
    }
    if ($datalayer['pagePostTerms']) {
        foreach ($datalayer['pagePostTerms'] as $taxonomy => $terms) {
            $datalayer['page-'.$taxonomy] = implode(',',$terms);
        }
    }

    return $datalayer;
}

2. that information from ipstack are interesting, but you should make the link protocol independent, so instead of
country_flag”:”http:\/\/assets.ipstack.com\/flags\/cz.svg”
there should be
country_flag”:”\/\/assets.ipstack.com\/flags\/cz.svg”
(ipstack supports both http and https)