1) I disagree, running an airline successfully a long time take a lot of careful planning and work. You navigate some tough times, like high fuel prices in the 70's and the aftermath of 9/11. An older airline may have taken longer to get there because initially demand is lower, aircraft are smaller and slower etc. What the score is, is some sort of assessment of the airlines at that time, as well as over time. I think someone who has kept an airline running longer deserves some recognition in the score, because it's not easy to have consistent success. Given the amount of bankruptcies in a game, which must run into 1000's. It doesn't take long to rise up the oldest airline list as a newer airline.
2) Disagree, ASK is a measure of sheer capacity, RPK is a measure of sales volume and LF is a measure of efficiency of converting capacity into sales. They are similar but each is a different airline metric measure, at least that's how I see them.
3) I can see this. Pax since start rewards consistent success of an airline, but I would suggest Pax (Previous), which reward more recent success as well as consistent success which helps balance the score better for newer airlines that are having great success.