Answer to "Flickering screen on low back light"I confirm that low temperture is the cause and I can explain why after the factory reset, the problem goes away for a while. Simply, after doing a factory reset / master reset, the phone gets very warm, that's a normal thing specially when the phone is reinstalling the system apps. As you can see, when you get your phone warm enough, your problem will vanish / will be reduced untill it gets cold again. When the phone is so cold, the problem gets worse. I tested this many times and it's 100% true. Now I think people who understand the hardware stuff will tell you that the connector is loose. Finally, we are waiting for a fix and untill that, keep your phone warm as possible as you can.
Answer to "Flickering screen on low back light"Currently I am using Twilight App for dimming my screen. I also did try that one in developper options then went to disable the auto adjust screen tone. For now it's working. I hope that this will help.