If your lady would've come to me to tell me what happened, i would have have swapped you (move her to your seat and you to her seat). Provided the flight was full, there isn't much you can do.
Having said that, at her request i would ask for the police to meet the a/c on arrival.
This guy's behavior was highly inappropriate; i am surprised she didn't inform the crew and she put up with it. It's good she told you after you landed as i assume you would've gone "off on one" to protect the wife, which is understandable given the circumstances.
Hope it never happens ever again