TinyMCE buttons that launch Ajax-generated forms

by using jQuery.ajax():

so, instead of that big form variable:

$.ajax({
  type: 'GET',
  url: 'admin-ajax.php',
  data: { action: 'get_my_form' },
  success: function(response){
    var table = $(response).find('table'); // you don't seem to use this "table" var
    $(response).appendTo('body').hide();
    // ...
  }
});

Now, the php:

add_action('wp_ajax_get_my_form',  'get_my_form');

function get_my_form(){
  // build your form here and echo it to the screen
  exit;
}