Leaning towards a control board issue and not just a thermistor problem. I don't suppose you know how CW determined it needed a new one and are you sure they replaced it?
As others have posted 36 to 38 in the fridge section is Ideal.
Going to give you a cheat to try, if you are at the bottom of the last fin on the right move the thermistor and holder over two fins toward the left and position the thermistor in the center vertically on the fin. This will make the thermistor react sooner as the fins are cooler the further left you go, that's why you see ice and condensation more on the left. This will cause the refrigerator not to run as long. You may have to make adjustments to get to what ever temperature you are after. This will not have any damaging effect on you refrigerator.