Found out that Pin 7 Digital Output is non-functional, so changed code to output HIGH/LOW values from Pin 2.
Cleaned up formatting.
Cleaned up circuit, so now it is more "breezy."
Tested the circuit with DC values ranging from -5V to 5V and it is functioning as expected.
To do: Fix AC functionality and also determine whether or not we want to compensate for the fact that voltages near the maximum voltage values of arduino are less accurate.