nice work!
to take the load off the back i would focus on engaging the hips sooner and keep driving them through which will keep your back at the same angle through the lift. Right now your driving your legs up to quickly and completing the lift in two movements...extending legs then lifting with back. You want to get down in position grab the bar, pull back then drive the hips through which will bring the bar up and keep you in proper position.
some techniques to get around this are doing some speed deadlifting. singles in the 65-75% range focusing on driving driving the hips through to raise the bar. Also if the hips need further development doing speed box squating, focusing on sitting way back, disengage hips for a fraction of a second then reangage to pull you off the bench and drive the bar up by driving hips through. This really helps with engaging them more explosivly on the deadlift.
Be carefull if you plan on adding a suit as it will cause you to drive your legs up even quicker getting you out of position.
Maybe start just a hair bit deeper, drive back like your pulling back at a 45deg angle and lift the bar by driving your hips through.
if you were in the proper position you could pull close to 700 now. I've got to get back into a meet and get my 700+ official as well.
let me know if the way i described this doesn't make sense.
Kabuki
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