You can BS 500lbs already?
What is your DL like? DL form varies wildly and as to how useful it is...
Guy DL 500lbs, but can only Clean 210-220 at the very best...his back was rounded and he is fast off the floro to hid thigh then slow
I DL 440lbs at my very best, only done it once. I Clean 350lbs+, I'm a lot slower then him off the floor but my 2nd pull is much stronger, coupled with the fact that I've been lifting for 12yrs...but my DL is no where near as strong as his.
The DL doesn't matter as long as you can maintain position in your Cleans. Squat more and get use to lifting.
STRENGTH IN THE POSITIONS IS FUNDAMENTAL AND KEY to lifting big weights.
Post up a video and I can tell you what your doing wrong.
Pull faster off the floor, really focus on using your quads to drive the bar off the floor, hips down, chest up, pull the bar in with your lats (meaning DO NOT BEND YOUR ARMS, but pull the bar with straight arms), DRIVE UP with your hips, the bar HAS TO BE PULLED IN CLOSE TO YOUR THIGHS to make use of your legs and power.
I wouldn't bother DL at all. I'd focus on learning to Clean/ Power Clean properly and getting your FS up.