Did you attempt to manually edit/enter these or allow the installer to do so??
Code:
  define('HTTP_SERVER', 'https://www.site.com');
  define('HTTPS_SERVER', 'https:/www.site.com');
Missing a "/" there

Code:
// * DIR_FS_* = Filesystem directories (local/physical)
  //the following path is a COMPLETE path to your Zen Cart files. eg: /var/www/vhost/accountname/public_html/store/
  define('DIR_FS_CATALOG', '/var/www/vhosts/site.com/httpdocs/shop/');
Are you sure that this is your correct path???
var, www, and vhosts are normally replaced with your actual variables for them


Code:
define('DB_SERVER', '127.0.0.1');
127.0.0.1 is usually "localhost" but is this is working leave it alone