I'm a fairly senior officer in the military and have a somewhat similar situation. Your COA depends on what your goal is. Do you want her back? Think about that one hard. If you do, then do nothing. Your W views you as the source of her unhappiness. If you expose this slimeball of a human and force them to break it off, you are again the source of her unhappiness. If you do this indirectly, she will still think it was you for who else has the motive.
If on the other hand you do not want her back, expose away. Start with your chain of command and let him get both barrels.
