The last challenge of the night was to run some wire, from the door, through the boot and into the cabin. This seemed to be a lot easier said than done.. since the Subaru engineers have been busy to ensure water stays away from the wiring harness. Hopefully I can explain this and give some justice to the poor guy who designed this part..
I first removed the screw which attaches the door hinge limit (someone help me out with the proper name of this part..), to free up some more space to work (turns out to be about 1/4"):
A few interior trim pieces were removed to gain access to the lower A-pillar/wheel-well area (under the dash, pics to come). This is where the wiring harness conduit starts between the cabin and the door.
To give a little more space, I removed the electrical tape that was wrapped numerously around the seam between the upper and lower 90 degree boot pieces.
Meanwhile.. squeezing the 90 degree boot on the door side, separates it from the door (to allow more flexibility for the wire to pass through). The above photo also shows the end of the boot, which actually runs all the way from inside the cabin, to completely inside the door. It seems that the top 90 degree boot is just for strain relief, since it just jackets an inner sheath (which is the part running continuously from door to cabin..).
Anyways, I pinched this "inner sheath" to slice a thin hole to stuff the overkill-sized wire into. Being extremely careful of course when handling a knife near the wiring harness. The hole cut, I greased the wire and began to push.. flexing the boot allowed the wire eventually to work its way down towards the cabin:
Well, all in all.. great success!