My ex watches every story I post. What is that?

Your ex appearing in the viewer list is a page event, not a spoken request to return. The list cannot establish regret, affection or deliberate monitoring. It also leaves you free to decide how visible you want your posts to be.

If checking that list keeps drawing your attention back, changing story visibility is a way to manage your own page, not a test of his reaction. There is no conversation here that requires you to send a message.