please don't take this as me being a dick, but if your lower back hurts from deadlifting, even lighter weight, perhaps you haven't learned the proper mechanics of the movement. Same goes with squatting.
To the OP, have you tried a sumo stance? Also, conventional pullers often have issues if their feet are shoulder width apart. Try bringing your feet in to where they are under 12 inches apart.
To the OP, have you tried a sumo stance? Also, conventional pullers often have issues if their feet are shoulder width apart. Try bringing your feet in to where they are under 12 inches apart.