Most Helpful Guy
It sounds like he was genuinely hurt by the break up.
Break ups are never easy, this might be a part of his mending process.
It sounds like he is trying to make you feel the way he feels.
It may be easier said than done. but I would try to ignore his foolish attempts to get under your skin.
send him a text back. "I'm sorry you're hurting. I really wish you nothing but the best. but these childish texts are kind of why we are no longer together. again I wish you the best."
kill him with kindness. he will quit sooner than if he sees he is getting a rise out of you.