Maybe take a new approach with him. Maybe you need to change the game because basically, I feel like we're waiting for him to make some grand gesture and THEN you'll react to it, whatever it may be. So how about you switch it up and keep him in the reaction mode and you continue to be proactive. What do you think?
Maybe text him back and say something completely friendly. Maybe before every interactiong with him you ask yourself "How would I treat my friend in this situation?" Or "What would I say to my very good friend in this conversation?" And treat him 100% like your good friend, not best friend, but good friend. If he were your good friend and you knew he was having a bad day you would text him what? I would probably say "Hey, I'm having such a great day I can give you some of my mojo to make yours better! As a matter of fact, I'm going to send you a blank text but it'll be full of good mojo!" Then do it, send him another blank text full of mojo and then follow it up with, "Feeling better? I hope so."
He is after all, the father of your children and if you really want him to think you are over him, you would really wish him the best. So maybe it's time to Act as If?