Does this school have a student bulletin or listing of policies online? My university has a very well-delineated policy for submitting a grade complaint – and it’s based on what other people have expressed here: if a grade deviates from the instructor’s own stated policy on his syllabus, then there is clear reason for protesting the grade. If there’s a policy outlined online, maybe you can just submit it in writing (rather than try to go in for meetings to explore options).
I teach at a major university, and I agree with your assessment – if the stated policy consisted of those percentages, then a single A- as 30% of the final average would not be enough to bring the whole final average down to A- range. He’s clearly not doing any calculations at all – just eyeballing the scores and putting down his own perceived estimates. Which goes against his own syllabus.