How to retrieve sumbitted data in modal
I'd suggest an approach which is not a solid, but you can get an idea;


Create modal with Ctools (may be this and this links can
help you to create it);
On form submission store the submitted data as array into $_SESSION;
reload the page with ctools_ajax_command_reload();


example:

// This is must be in ctools modal callback. Read modal.html file in ctools/help directory
if (!empty($form_state['executed'])) {
  $commands = array();
  $commands[] = ctools_ajax_command_reload();
}



Alter the content add form;
add #default_value to the fields, e.g.: '#default_value' =&gt; isset($_SESSION['modal_data']['field_1_value']) ? $_SESSION['modal_data']['field_1_value'] : '';
at the end of the content add form just unset the $_SESSION data, e.g.: unset($_SESSION['modal_data']);