回复：我当时是这样做的。

What you did "如果他按照我的要求把分数改成A，没有人会有任何损失，但如果他不改，我就义无反顾的搞到DEAN甚至校长那里去。" is illegal in any country including China. Such act is called "threaten someone to achieve the benefit".

Your professor was so nice to you. He gave you A not because of your threatening, but he was helpless on you, a Chinese!