I fixed screen flickering. Just replaced IntelBacklight.kext with a new one.
Also I added EmuVariableUefi-64.efi driver to preserve brightness, volume level after reboots
One thing that bothers me then happened. After several restarts I had kernel panic at assertion in AppleIntelFramebuffer.kext. That was due to DVMT value magically reverted back to 0x1 and I had to set it to 0x3 again. After that I cannot see Nvidia chip in System report now, so I think it's disabled now.
I looked for my wireless card and discovered that it's not 1/2 miniPCIe but NGFF. I suppose Dell DW1560 (Broadcom BCM94352Z) is the only card that would work in my case?
I updated my first post.