HD3000 (Laptop) - No backlight unless connected to external display, which yields a gray screen?

Hi!

I have made a few posts in the last few days regarding a Dell Inspiron N7110 on High Sierra... The issue I'm having right now is that the system boots - but I can't install, mainly because the backlight turns off, and when I plug into an external display, I get that gray screen the comes before the installer - but no installer window. Also, when I plug in the display, the backlight of the internal display turns on... I feel defeated, I have been trying to get this working on this laptop for quite a while...