I WILL stab him then...there used to be two guys she was cheating on me with, but the bard from riverwood died in a dragon attack.......in fact, riverwood is becoming somewhat of a ghost town...the blacksmith went a-wall on me when I killed a chicken and harvested a potato plant...he came running outside in the rain with his fists...i was forced to kill him.
Wait until you see him in your house again, then follow him out. Wait until he's either far outside the city, or in a quiet room.
Then proceed to stab him multiple times, strip his corpse, and leave it in some sort of highly embarrassing position ^_^