Hi all!
Summer is finally here, so ferrix has had some time to work on the portable.

You'll find the pictures of the cable he made attached to this post. 
However, we still have two major problems here:

1. When the display is plugged in, the system doesn't even attempt to boot - we think there might be a short somewhere that we still haven't figured out, because current consumption goes up to 3A and triggers the CC led in the power supply.
2. When the display is disconnected, the system actually attempts to boot: we can hear it chime successfully most of the times, but as soon as it chimes the current level drops and the system shuts down. However, this is not happening predictably: if we only leave the yellow cable (pic below) connected the system tries to boot, chimes and shuts down. If we also connect the red cable, current goes instantly to zero and the system dies - if it's chiming, that produces a sad mac chime.

I'm also uploading reference videos here, here and here.

As always, we really appreciate your suggestions - we're not really experienced with portables, so any thought on this will be great!