Going from 405-495 in a short time is highly unlikely, even if you are realatively new.
For some reason, I can't get your video to come up. Alot of people will tell you something wrong with your form. The thing that I've learned about form is that there is no perfect form but there is a form that is perfect for you. You have to reinforce your form and work it. Unless its something like straight legged with rounded back and then you need to change. You are setting yourself up for disappointment and frustration by putting a timeframe on your goal. It might take you a year to reach 500 or it could be 3 months. Either way be happy with any progress you make.
Now one thing that really helped my Deadlift, actually all my lifts, was adding in a separate back day. I focused on pull ups, light high rep rows, face pulls, etc. Things to work the middle and upper back. I also think at your level of strength you would be better off not specializing on one lift. Your squat strength could help your Deadlift.
Geeze I ramble!