I am planning on running this on a 3.6V circuit and my prototype scrolls through 15 20mA led's.
Will this chip be able to handle running 4 led's on each pin? (80mA?) while (on rare occasion) fade all 60?
The datasheet says:
60 mA (VCC < 3.6 V)
120 mA (VCC > 3.6 V
It doesn't say what happens when VCC=3.6V but 80mA is right in the middle...
You're planning on having the chip dissipate about 0.5V per channel (3.6 minus 3.1). 0.5V*80mA*16 channels=640mW. That's well within the limits for power dissipation.
You should be fine.