2. how did you calculate
fill a full tank. reset milage to zero. drive some 300 to 400 km, write it down. refill the tank until full. this time, the amount of gas that refill the tank is the amount of gas that run that milage. divide the gas by milage, you get correct gas consumation.
3. if confrimed problem, drive to a Toyota dealer, tell them what happens, request for a through check.