Could this also be interpreted as: You can change your ticket less than 30 days before your original departure, as long as the new departure date is more than 30 days away from the time of re-booking? After all, it doesn't say "30 days before originally booked departure [date]".

I would also recommend to have the ticket refunded, if that is possible (As it should be, reading through the rest of the conditions that you quoted).