I am doing my best to remember that the OW is nothing to me. This is one of the only things that gets me through their phone calls and texts, expecially when we're in the same room.
He calls his OW and text her right in front of you???
You need to learn about setting and enforcing boundaries. You can't force him to end his affair, but you darned sure don't need to have your nose rubbed in it. That's simply direspectful!