In order to do this you need to use meta_query instead of meta_key and meta_type.
For more information about ordering by a custom field see the last code example in the order by section here https://codex.wordpress.org/Class_Reference/WP_Query#Order_.26_Orderby_Parameters and this page https://make.wordpress.org/core/2014/08/29/a-more-powerful-order-by-in-wordpress-4-0/
