Freezer Coil Not Getting Cold - Kenmore 596.58692890

We have an older Kenmore side by side refrigerator. Recently the freezer cooling was sporadic and it would sometimes be very cold, other times ice cream would be liquid, etc. My daughter noticed at one point that the defroster element was getting cherry red through the vent holes. During this period of odd behavior, the fridge was actually getting colder, enough to cause ice crystals in the milk.

4 days later, it is no longer cooling on either side. Both the condenser and evaporator fans seem to be running fine. The compressor is running, but feels pretty warm. I have cleared as much dust as I could from the condenser, the design of this unit really makes it difficult to access it for thorough cleaning, as it is sandwiched between the base and a solid plate on the bottom.

Oddly, the supply line to the freezer coil is frosting over all the way up to the coil, but none of the coil is cold.