Have you contacted the dealer principle, the boss of the above arrogant individual?
Is this the only contact in your country? Is there no other dealerships you could approach.
Getting to the head of any large organisation is always fraught as the 'correct channels' are always via your local representative. Is there a central office in Switzerland you could approach, or is this whom you have already dealt with?
I think I might personally ring the offices in Brussels asking for the customer services department, or requesting their direct contact details.
I'd imaging contacting any other centre, including Japan would be fruitless, or at best, extremely longwinded and delayed.
To be honest, if the dealership are attempting to correct the issues under warranty it's going to be a struggle.
Is it possible to reject the car under statutory buyer's rights?