[COLOR="Blue"]The question I have is would the cooling fan (in the freezer on an "over/under") not running cause the refrig part of the unit to run warm?[/COLOR]
Yes it would. It is required to pull air through the evaporator coils to cool it efficiently. Also it circulates the cold air into/through the fresh food section.

[COLOR="Blue"]Also, can anyone explain to me the correlation between the defrost timer and terminator and the same problem?[/COLOR]
Not sure what you mean by "terminator"

[COLOR="Blue"]Would the timer just make the frig run constantly, or is there another function of it (sans the actual defrost timing) like one that connects a circuit to the heater when it goes into defrost?[/COLOR]
The timer controls the defrost cycle frequency.
Found he following confusing "like one that connects a circuit to the heater when it goes into defrost?" because that is what a defrost timer does. It shuts off the compressor and the fans and turns on the defrost heater.
The timer cannot make the fridge run constantly. The compressor is controlled by the thermostat.

For instance, if you have a defrost problem the evaporator coils frost/ice up to the point where the evaporator/freezer fan cannot pull air through them. The temperatures in the unit rise, the thermostat senses this and turns the compressor on. But due to the inefficient cooling the unit cannot get down to the compressor's set point so the unit runs continuously.

FYI: the defrost thermostat (terminator) opens just above freezing.
The defrost timer has a set time for defrost (usually around 30 minutes) but lets say that all the frost is off the evaporator coils after 15 minutes. Then the defrost thermostat will open shutting off the heater for the rest of the defrost cycle.

This prevents excessive heat in the freezer that would melt the food.