Good job filiming, and I like the background music!
Like the other dudes said, your back rounds WAY too much for safety. What always helps me is visualizing the lift. Meaning that I get the weights set up, do all that jazz, and then sit there for a second and see the lift. I then walk over to the bar, set up my feet, attach my straps, then lift. And when I lift, I think about DRIVING my feet through the floor, not lifting the weight. This simple visualization will make a world of difference, trust me.
Also, I'd recommend getting some wrist straps. They take the pressure off your grip and let you focus on using your back/legs more.
As far as Hungry4More's recommendation, sumo DL's are awesome. For starters, people can usually lift a bit more with sumo variations. Also, it's just more natural feeling for some. Also, it's more of a hip exercise. In fact, I feel conventional DL's in my back, so I've moved DLs to back day. If I wanted to do a DL variation on leg day, I'd do sumo or even trap bar. Basically sumo DL's are just another way of doing the movement.
Just focus on crushing your feet through the floor man! Good work though.
Oh and Trav, holy shit at that 700 lb raw DL! NO STRAPS! I wouldn't want to shake that dude's hand.