I'm a bit late to the conversation, but as he's a director, have you though of contacting his PA? (He may have his own or share one with other directors). I find them super helpful for making appointments: they have access to the calendars and often do all the setting up on the behalf the directors - they just show up and talk. And I agree wholeheartedly with Tiffany: make it just one concise call and send him an outline of what you want to ask him ahead of time.
