P: Color temperature below 2000K

Thanks Alex. NX2 also has very constrained temperature ranges - I never understood why one can not adjust "all the way" in both directions, whatever that would mean...

Yes. It's a temperature of the ideal black-body radiator, it can be 0K. The candle light is starting from ~1500 K, the dark red glow of the heated metal have temperature about 800 K.

I don't understand enough to know why there is any limit at all. Is there a 0K?

I tried to use calibration controls, but didn't got results like in Capture One. Maybe I did something wrong. The same for profile. It worth to try again.
But the point is the color temperature is much more user-friendly control. And if we have temperature over 20,000K, why we can't get lower than 2000K? Defenitely this is artificial limitation.

You can also adjust temperature using the camera calibration section. In fact, I know of one person who prefers using RGB over temp/tint, and uses cam-cal exclusively for white balance adjustment.

One option: create infrared preset that has a cool bias to cam-cal, then go the rest of the way with the temp/tint sliders.

Note: presets lump the camera profile in with the shadow-tint/rgb sliders, but you can take the camera profile out using a text editor (then restart Lightroom), to have an rgb preset that will work with any profile.

Another option: create a DNG color profile for infrared.