Fine tune node permissions

The default CRUD + view operations on nodes can be fine tuned by using

/**
 * Implements hook_menu_alter().
 */
function mymodule_menu_alter(&$items) {
  $items['node/%node/edit']['access callback'] = '_mymodule_node_edit_form_access';
  $items['node/%node/edit']['access arguments'] = array(1);
}
 
function _mymodule_node_edit_form_access($node) {
  $type = is_string($node) ? $node : $node->type;
  if ($type == 'webform') {
    // Do some additional checks.
      return FALSE;
    }
  }
  // Otherwise use the default access rules.
  return node_access('edit', $node);
}

Note that this can be achieved in some cases by simply using hook_node_access() ...

Display errors - WSOD

The bootstrap override the values you could set to display error ad the reporting level. To be 100% sure everything is printed out when something fails in a blank screen (wsod), make index.php like this:

Properly render a field

Drupal offers a few (sometimes complicated...) solutions to output a field. Lets take an example with a date field.
To display the full rendered field: field_view_field()