Adjusted minimum brightness, got black screen often now, why?

Lying in bed it's nice to have dim lights, so I wanted to adjust the brightness of the display below stock minimum, and found a guide which said:

Go into: sys/class/leds/lcd-backlight
In that folder open «brightness» as a text file, and change the value from «10» to «1».

The only problem was my phone already had the value set to «1», so I thought, let's set it lower, let's set it to «0.5», so I did. And not long after the phone got a black screen, and I held all buttons to boot, and when it was rebooted everything worked fine, just fine. Except that I now, once in a while, get a black screen.

I'd love to get help to fix that. If you have any ideas, please let me know!

To troubleshoot, I used ES File Explorer again, and opened the said «brightness» file and I saw that it's been automatically (I suppose) set back to «1».

But I have this folder called:
sys/class/leds/lcd-backlight-nits
And in that folder the «brightness» is set to «0» (not 0.5)
Not sure if that "nits" folder is new, or autogenerated or related to the problem.

 

It is rooted with CM13, a HTC M8, and the issue is that I can't go below the minimum on the pull down notification bar. Manufacturers have set a minimum higher than the real minimum, so it's very nice to go below that when in bed with someone else, and besides I think it feels better for the eyes with less light.

So there's a workaround to edit that brightness file in /sys/