Pager not working when $form['table'] is called with AJAX

For a statistics page I let users select the right file in a select list. After that I generate a table with stats. This table also has a pager (that worked without the ajax part).

Now I did everything in an ajax callback, when I now want to click on next page the URL is: http://localhost/drupal2/system/ajax?page=1 and that doesn’t work ofcourse.

My code:

function push_notifications_theme() {
return array(
'push_notifications_form_table' => array(
  'render element' => 'form',
),
);
}

function push_notifications_form_table_form($form = array(), &$form_state) {
$form = array();
// $id = $_GET['id'];

$qry = db_select('push_notifications_api', 'pt');
$qry->distinct();
$qry->fields('pt', array('app_name'));
$qry->orderBy('app_name', 'ASC');
$names = $qry->execute();
foreach($names as $record) {
$options[$record->app_name] = $record->app_name;
}

$form['title'] = array(
'#type' => 'fieldset',
'#title' => t('Application statistics'),
'#description' => t('Select an application below to see the statistics.'),
'#tree' => TRUE,
);

$form['title']['changethis'] = array(
'#title' => t('Application Name'),
'#type' => 'select',
'#options' => $options,
'#required' => TRUE,
'#ajax' => array(
  'callback' => 'push_notifications_form_table_form_callback',
  'wrapper' => 'replace_textfield_div',
),
);

$form['replace_textfield'] = array(
'#prefix' => '<div id="replace_textfield_div">',
'#suffix' => '</div>',
);

if(!empty($form_state['values']['title']['changethis'])) {

$appname = $form_state['values']['title']['changethis'];
$id = db_query('SELECT app_id FROM push_notifications_api WHERE app_name = :app_name', array(':app_name' => $appname))->fetchField();

$form['replace_textfield']['id'] = array(
'#type' => 'fieldset',
'#title' => t('@appname: Push notifications', array('@appname' => $appname)),
'#description' => t('Newest push notifications are on top.'),
'#weight' => 10,
);  

$go_back_link = array(
'!link' => l(t('go back to the overview'), 'http://localhost/drupal2/admin/config/services/push_notifications'),
);

$form['replace_textfield']['goback'] = array(
'#type' => 'fieldset',
'#title' => t('Go back'),
'#description' => t('If you want to view stats from other application you can !link', $go_back_link),
'#weight' => 25,
);

// $query = db_query('SELECT * FROM push_notifications_messages WHERE msg_appID = :app_id ORDER BY msg_timestamp DESC', array(':app_id' => $id));
// $qCount = db_query('SELECT * FROM push_notifications_messages WHERE msg_appID = :app_id', array(':app_id' => $id))->rowCount();

$query = db_select("push_notifications_messages", "n");
$query->fields("n", array('msg_id', 'msg_message', 'msg_receiver', 'msg_device', 'msg_appID', 'msg_timestamp'));
$query->orderBy('msg_timestamp', 'DESC');
$query->condition('msg_appID', $id);
$query = $query->extend('TableSort')->extend('PagerDefault')->limit(15);
$result1 = $query->execute();


$form['replace_textfield']['table'] = array(
    '#theme' => 'table',
    '#header' => array(t('Message'), t('Device'), t('Token'), t('Date')),
    'rows' => array(),
    '#weight' => 15,
    );

foreach($result1 as $key => $result) {
    $form['replace_textfield']['table']["#rows"]["'r$key'"] = array(
        'c1' => array(
            'data' => array('#type' => 'item', '#markup' => t('@message', array('@message' => $result->msg_message))),
          ),
        'c2' => array(
            'data' => array('#type' => 'item', '#markup' => t('@device', array('@device' => $result->msg_device))),
          ),
        'c3' => array(
            'data' => array('#type' => 'item', '#markup' => t('@token', array('@token' => substr($result->msg_receiver, -50)))),
          ),
        'c4' => array(
            'data' => array('#type' => 'item', '#markup' => t('@timestamp', array('@timestamp' => date("d F Y H:i:s", $result->msg_timestamp)))),
          ),      
      );
}


$form['replace_textfield']['pager'] = array('#markup' => theme('pager'), '#weight' => 20);

}

  return $form;
}

function push_notifications_form_table_form_callback($form, $form_state) {
// The form has already been submitted and updated. We can return the replaced
// item as it is.
return $form['replace_textfield'];
}

function theme_push_notifications_form_table(&$variables) {
// Get the userful values.
$form = $variables['form'];
$rows = $form['rows'];
$header = $form['#header'];

// Setup the structure to be rendered and returned.
$content = array(
'#theme' => 'table',
'#header' => $header,
'#rows' => array(),
);

// Traverse each row.  @see element_chidren().
foreach (element_children($rows) as $row_index) {
$row = array();
// Traverse each column in the row.  @see element_children().
foreach (element_children($rows[$row_index]) as $col_index) {
  // Render the column form element.
  $row[] = drupal_render($rows[$row_index][$col_index]);
}
// Add the row to the table.
$content['#rows'][] = $row;
}

// Redner the table and return.
return drupal_render($content);
}

Screenshot of result: