Converting an ADC value to equivalent Temperature?
1) Change R8/P1 to get the voltage range you want for the temperatures you want to measure.

2) Set P2 higher to match the values to the range of your ADC.

3) Set sampling time no higher than X times the time constant of your system including sensors. Find a good number for X depending on the requirements of the system. You may however want to average a number of rapid samplings to reduce noise/add bits.

4) A combination of lookup table and interpolation usually works well. Build an excel sheet to show the error of the approximation - massage it until it works for your application.