Also says 80mA Absolute Max.
With a voltage range of 3 to 3.4V.
Keep in mind the resistors will also have some variance.
I would design for worst case voltage of 3V as that would have highest current flow, and use the midpoint of the suggested current of 65-75mA:
(9-3-3)/70mA = 42ohm.
TIP120 also has some voltage drop across it, 2V typical for 3A of flow:http://www.adafruit.com/datasheets/TIP120.pdf
So say it was only 1V even:
(9-3-3-1)/33 = 60mA
So the 33 ohm should have been fine, as long as each string had a resistor in series.