Good survey ^ and good luck for your dissertation
one remark:
I think the question in # 15 is related to codeshares:
It is OK that another airline fly the route instead of the airline I booked with (e.g., Iberia operates the route of BA, or United instead of Lufthansa, etc.)
It might be an advantage to use the term "codeshare".
And sometimes, it was a little bit difficutl to focus on one answer, as more than one answers apply ....
Indeed, the fare is important, but I tend to use the cheapest fare an airline of "my alliance" offers on the route I want to fly, regardless of travel time and number of connections