1) If I use the same resistor with a higher voltage, I will put more current through the LED.

It is now time for you to start testing, and compare the measurement results with datasheet.

Do you have adjustable powersupply?

Get about 50 ohm, more ohms better to save the LED.

Adjust max. voltage to 5V, if 50 ohm R1.

Start from 1V, 0.5V increments to 5V.

Measure every step from LED and R1.

If your PSU don't show amps, you can calculate it with two units you know for sure.

Draw a curve, calculated amps agains the measured voltage OVER THE LED, that shows you the non-linear LEDs effect in the circuit.

Then double the R1, increase the PSU voltage 7V and start measuring the voltage over LED, notice the brightness, draw a curve, calculate the current...

Cheers,

Kari