Just wanted to come back and report that after replacing the evaporator fan the fridge is now back up and running perfectly.

For the sake of anyone else reading this later, trying to troubleshoot a similar scenario, do NOT make the same mistake I made. Just because you see the evaporator fan spinning does NOT necessarily mean it's in proper working order. Take it out and check for proper supply voltage as well as resistance across the fan motor itself. (See Gene's excellent post here for details.)

And by all means, if you have a blown motherboard (aka main control board), check the evaporator fan as well since a bad fan can damage the board. My original board was definitely, visibly bad, but I suspect the original problem all along was the evaporator fan.