forget the toothpaste, since your lcd looks wasted, you may try a more agressive polish. I've had very good result on a mpc2500 screen with a plastic headlights polish.
http://www.amazon.com/Meguiars-Plast.../dp/B0000AY3SR
this was purchased for my old BMW Z3 but turned out to be quite effective on the scratches I had on my MPC.