re: Point by point.
The "proper purpose of taxation" and its "functions proper to government" are not for you to decide. That is to be determined politically, not by what is convenient for any one class or group.
Obviously there are standards of judgment on the role and power of government above and beyond "political" decision systems, otherwise if a majority of the country voted slavery back in, I could have no objection to it.
Most political decision making is already driven by special interests.
Airports are paid for by a wide variety of fees and taxes on airport users, of which private jet operators pay their share. So do you when you buy an airline ticket.