Honestly i don't see the big deal with changing the syllabus half-way through. I doubt he did it just to 'get you'. The teachers here do shit like that all the time. They often times curve AGAINST you, and you don't know what your final grade will be until after the class is over. It depends on the distribution -- often times in a bi-modal distribution we have teachers who lower the high grades and raise the low grades to make it more bell shaped and less bi-modal.

The med school classes here curve you based on other students (which i find very reasonable if they average and throw out the outliers).