Great - We it’s what I had feared 😫
The back edge is where the logic board sits, to add to it the heat sink and the CPU sit quite high! Right under the bang. I’m suspecting the pressure of the bottom cover is messing you up. Does taking the bottom cover off change things?
Let’s see if the video signal is still getting to the display. Press a flashlight against the lids Apple logo (a poor man’s backlight) are you able to see the faint image of your desktop?
The second test is to check the hall sensor which is located on the logic board on the back side along the edge between the ports.
An easy way to test is to take a steel paper clip sliding it along the displays face the magnet within it should tug on it slightly, now use some masking tape to mark the location so when you close the lid you can carry the mark over to the uppercase. Now using a small rare earth magnet slide it across the spot did the display turn on and off as you passed the sensor, don’t go to fast.