Since your resistance coil is only at .5, I would suggest Samsung INR 18650 -25R 2500mAh or LG HE4, why not VCT4?
You're limited by your device specs, 30 watts and internal circuits limitation.
So even at 30 watts, .5 resistance, you're only going to draw close to 8 amps (7.7)
So you might as...