Make laughter the ridiculous thing you do. Maybe start off with laughing at his intrusive questions as if he’s making a combination joke/rhetorical question. As he keeps pushing, laugh more and more. At first it can be like you’re laughing at a mildly-funny pun. The next time, consider it a funny joke. Maybe the next time, it’s the funniest joke you’ve ever heard. Keep escalating until you’re laughing maniacally every time he pries. Don’t quit when he finally walks away. Follow him and laugh more and more annoyingly. Until he quits prying.