You agreed the change of instructor so, to a point, there’s no comeback there. Apart from having a word with the boss as ROG has suggested. In the unlikely event that the instructor is registered, you have recourse through the appropriate register as a matter of professionalism.
But the change of test centre I would see as a material change to the original contract and I don’t see why you have to accept this. Once again, a word with the boss is needed.
I definitely wouldn’t ditch the course. Just work hard and try to rise above this guy’s attitude.
Chin up, work hard and get the test passed.
Pete 