I am going on the assumption that you would have previously fried something if there was a short in your Portable motherboard/display.  Hopefully your bench power supply POP was a coincidence.

I am taking a guess at this but I could see the difference in amperage when the screen goes out because it's drawing no current and the the spike to 0.6A you are seeing is the display firing up and then going dim.   I'm not sure if 0.1A is normal for just the motherboard.  Someone else will have to chime in here.  

Now that you have the cable properly doe, is there any difference if you disconnect it?  If it's soldered, it will be hard to do but just checking.