PDA is not a function of AOA or pitch angle. PDA is the result of engine wear resulting in more fuel being required to produce the required thrust and increased drag that results from airframe damage/pitting in service. The majority of the PDA is from engine wear.
Trying to draw a relationship between CI and LRC is not a logical or realistic concept. LRC is a fixed value above MRC and depending on the individual operator costs on a route the CI that generates the same speed profile as LRC will be different from operator to operator and route to route.
As for the discussion about pitch angle and AOA in cruise and the urban legend of "wasting fuel" due to increased drag, it is important to remember that in cruise the largest portion of drag results from ramming the blunt object through the air and is a function of the square of the speed.
Sadly, CI is one of the most misunderstood concepts in aviation and we devote the least amount of training footprint to increasing pilot knowledge on what it is, how it works and how to fly efficiently.
The Airbus publications "Getting to Grips" with CI and Fuel Economy offer a wealth of information, but need to be tempered with the fact they were written at a time when the price of fuel was significantly less. This skews a number of the graphs and nullifies many of the statements concerning lower cost index values.