My lockout is my weakpoint as well. Exercises that actually transfer over to more lockout power are tough to find. Ones that have worked for me are rev. band deadlifts, VERY heavy RDLs, Speed pulls, opposite stance pulls, rack pulls for 5-8rms 2inches above and below my sticking point, and anything that hammers the upper back. Your grip looks solid and your speed off the floor is awesome. You are quad dominant though and its shifting the emphasis away from your hamstrings and hips. That fact that you are moving that much weight with that much ease from a quad dominant postition is pretty impressive. You have a shitload of unlocked potential.