Re: lower back issue in heavy deadlifts
Set your ego aside (we all have it) and do your deads at a weight that allows you to do them right. Don't move up until you can routinely and effortlessly maintain proper form, and, when you do move up in weight, don't do it by much. If you move up and can't keep good form, reduce the amount by which you have moved up, or even go back down to where you were before.
Technique-wise, I agree with everything Robert said.