well vga cables are shielded but not a lot. cause they dont really need to be. u can wrap the entire cor din a few layers of electrical tape
or have the vga running else where
since u have SO much extra i'd recomend running it over the door instead of under.. (if u have the room) this should help.. then around your wires/HU i'd wrap it in some electrical tape
also kb/mouse doesnt carry much of a current so it wouldnt do squat
hope i helped?