Open pop on click of custom action and get filled data
I'm not sure what your Question is exactly and what your expected outcome is but to create a Modal you can use this HTML

&lt;div id="my-awesome-modal" class="modal"&gt;
    &lt;div id="modal-body" class="body"&gt;
        &lt;header class="header"&gt;
            &lt;h2&gt;My Awesome Modal&lt;/h2&gt;
        &lt;/header&gt;
    &lt;/div&gt;
&lt;/div&gt;


and via JavaScript you can show it

//create it
var modal = new Garnish.Modal($('#my-awesome-modal')); 
modal.show();