how can i access a node variable inside of theme_preprocess_page function?
Have you tried field_view_values() and field_get_items() 

function mytheme_preprocess_page(&amp;$variables) {
    if (!empty($variables['node'])) {
      $output = '';
      $node = $variables['node'];
      $items = field_get_items('node', $node, 'field name');
      foreach ($items as $item) {
        $field_output = field_view_value('node', $node, 'field name', $item);
        $output .= render($field_output);
      }
      // Set $variables with the value you need.
    }
  }


Explained in here how to access node variables in region preprocess function? 

I think you should also be able to use entity_metadata_wrapper as follow

$node = $variables['node'];
$wrapper = entity_metadata_wrapper('node',$node); 
$libStatus = $wrapper-&gt;field_feature_library_status-&gt;value();