That's a horrible situation to be in!! I can't imagine what that must be like, having to see him at work! Do you have the opportunity to talk about this to a therapist? They might be able to help you sort out possible ways to cope/address the situation.

For what it's worth, I had intrusive memories that were distracting me at work. So I taped a nickel to the inside of my elbow. Every time I bent my arm, it hurt. The pain pushed back the memories. After day 2 of this, I had to stop because arms were experiencing spasms, so all-day-long might be too long for this sort of thing.

I'm sorry your are experiencing such distress. It's a distressing situation. You are an amazingly strong person for showing up to work every day! You have my utmost admiration!