I know you didn't have the 'it's over' talk, but moving out is a pretty big FU. It's fair to assume that when a partner moves out, the relationship is over - unless they say otherwise.
Thing is, neither of you owe each other anything now. He doesn't have to stay true and you don't have to tell him who told you stuff. Just call it even and cut him out of your life
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.