Which hook for code after a node has been deleted from the DB?
There isn't one. If you look at node_delete_multiple(), which node_delete is a wrapper function for, you can see that the only hook invocations (the above hooks) are triggered before the DB delete statements. 

If your Drupal site only allows deleting through the node/$nid/delete form, one alternative to a post-delete hook is appending a submission handler to the node deletion confirmation form:

function MYMODULE_form_node_delete_confirm_alter(&amp;$form, &amp;$form_state, $form_id) {
  $form['#submit'][] = 'MYMODULE_node_delete_confirm_submit';
}

function MYMODULE_node_delete_confirm_submit($form, &amp;$form_state) {
  //@TODO: Post-node-delete code here
}