The reason your code does not work is that the if-statement checking isset( $_POST['wp_cfc_save_meta_box']) never evaluates to true. Your code generating the submit button,

<?php submit_button( __( 'Save as Pending' ), 'secondary button-large', 'Publish', false ); ?>

yields the following HTML:

<input type="submit" name="Publish" id="Publish" class="button button-large" value="Save as Pending"  />

WordPress’ submit_button function takes several arguments, the third of which is $name. This is used as the HTML name attribute of the submit button input element, and is passed in the $POST array on submission of the form. Thus, instead of the desired $_POST['wp_cfc_save_meta_box'], $_POST['Publish'] becomes set. To tackle the problem, change the $name$ parameter to 'wp_cfc_save_meta_box'. This yields

<?php submit_button( __( 'Save as Pending' ), 'secondary button-large', 'wp_cfc_save_meta_box', false ); ?>

By the way…

You could make this a little bit prettier and utilize the post_submitbox_misc_actions action to add the button to the original Publish met box instead of a custom meta box.