The LED function is possible with the LM822 and LM823. As described on the datasheet the LED is a factory option that has to be specifically ordered and is disabled by default.
For enquiries about ordering this variant please contact a member of our sales team: https://www.lm-technologies.com/contact/
If I apply 5V to the led(Vf=2V) with 15mA flowing through it, is a 200 Ohm resistor the right value to use?
This would be correct.
Driving the LED with 3.3V instead of 5V, what resistor should I use?
Please refer to the Relative Luminous Intensity VS Forward Current as shown in the graphic, you can design the resistor accordingly.
3.3V / 6mA = 550 ohms
3.3V / 15mA = 220 ohms
3.3V/ 25mA = 130 ohms