Doctor Cruces
i can not answer your first question but I hope I can help u with the second one.
basically " CI = cost of time/cost of fuel ".
so if an airline is facing considerably high charges of time ($/hr) ex. crew and operating costs, than the fuel charges, the cost index will be a higher value and hence will allow the FMC to calculate a low time flight profile by using higher speeds for different flight profiles.
Also if the cost of the fuel is considerably higher than the time costs, the CI will be a small number. That will allow the FMC to calculate the most fuel efficient flight profile regardless of the speed and range.
I hope that helped.
vicky