It sounds like your planning on having to defend yourself after your split is more widely known. That it's you vs him and the winner is whoever collects the most friends. It's not a battle and can't be if you choose to mindfully rise above it all. Simply put, don't behave the way he paints you to the world. You can't out argue a manipulator. They are masterful at taking your words and actions and using them against you. Stop giving him ammunition to use against you by not engaging at all. If he and the friends he collects in the end prefer to gossip and run rumors, you haven't lost anything worth keeping.

Win by being happier without him than you are with him. Practice these words "I understand that he is saying things about me. Thank you for letting me know. I appreciate your concern for my happiness." And let it go. Anyone who was trying to get you to react (aka manipulate you) isn't someone to be friends with. Anyone who tries to keep talking about it (aka manipulate you) needs a reminder that you are choosing to be happy despite what rumors he starts.

Prioritize being happy and let being right go. After all is said and done, do you want to have happiness or righteous indignation as the good thing in your life. You can't have both in a conflict.

All the best to you.