At your level, don't worry too much about rack pulls. You simply need to get stronger at the basic lifts (SQ, DL, BP, overhead press, rows). You can deadlift once a week, doing 1-5 reps per set. Again don't work up to an absolute max, simply get some good quality "heavy" reps (whatever weight is heavy for you). Do some back raises or something similar for higher reps and do some heavy ab work. About 90% of the time I've seen people having lockout issues with the DL, it's because they get rounded over and are in such poor position by the time the bar gets past the knees they have no chance to finish the lift.
Don't worry too much about weak points at this time. Everything needs to get stronger. You also need to make sure your technique is good and you should always seek to improve it.