Reload page after applying commerce coupon
One solution here is to add a custom JS behavior to your module that looks for the AJAX callback context of applying a coupon. Upon such context, you can refresh the page or update the DOM as you see fit.

(function ($) {
Drupal.behaviors.mymodule = {
  attach: function (context, settings) {

    //Look for the context of a coupon form AJAX callback
    //If there's no error message, assume successful coupon application
    if($(context[0]).attr('id') == 'commerce-checkout-coupon-ajax-wrapper' &amp;&amp; !$(context[0]).find('.messages').hasClass('error')) {
      //@TODO: Reload page or other JS to refresh coupon usage
    }
  }
};
}(jQuery));