It doesn’t really matter what happened in his past...he’s your ex. The end.
It’s a little odd that your friend came at you about him calling her. You’re not responsible for his behavior. She blocked him. Again, the end. You didn’t need to contact him to tell him not to call her...again, he’s not your responsibility.
If it were me, I would be less concerned about the past deception (in which she participated) and more concerned about how this revived friendship seems all tangled up with the ex. And FWIW, he’s awfully jumpy about what was supposedly just a friendly lunch.
If it were me, I wouldn’t want the drama. Some friendships end for a reason, yes?