总监，总统，总裁 and other similar words
They're really confused, and often changes meaning according to the context. Here're my opinions:

总统 is the most clear one here, as you said, means the president of a country.

董事长 means chairman of the board.

总裁 (president), according to my experience, usually used for the CEO of a large company, which has a number of subsidiaries. BTW, 总经理 is often used for CEO too, but usually for a small or one-tier company.

总监 is used for a chief officer of certain field, such as 技术总监 (CTO).

主任, and 主管, means director, usually used for the people who are primarily responsible for an organization or department. Such as 财务主管 (financial executive), 教务主任 (dean of students).

领导 is a generic salutation for your superior, immediate or non immediate.

老板 (boss) is a generic salutation too, usually used for the top of your company, such as 总经理 (CEO).