The wire is installed as I suggested and everything is working fine.
I drilled to just penetrate the freezer inside metal, then widened the hole to 1/4", then probed the insulation with an awl to push any possible wires aside, then hammered the awl to penetrate the metal back, used the penetration as pilot to drill the back. Taped a neutral wire up the back, then siliconed the wire in the hole inside and out. I attached the new white neutral to the white side of the defrost bi-metal cutoff switch.
For those curious about the original weird symptom of the evaporator fan only running with the freezer door open, thermostat off, and dim light bulb. The power was supplied by the door switch, through the light bulb (very dim), then "backward" through the evap fan finding a return/neutral through the red wire (from thermostat) that normally triggers the compressor. There is only about 1.7 ohms through the red wire compressor start circuit back to neutral on the terminal block. The compressor did not start with that smaller current running through the start circuit (maybe the relay coil?).
Thanks for all your help and suggestions.