Yes bro, its great for your overall body growth. I do deadlifts once every other week because it is so taxing on my body that everything gets sore. I never go below 6 reps because when you do you open yourself up for injury and then your screwed for a while. The 6 reps I do though are to failure so I put everything I have into each one.
The most common mistake I see other than poor posture is letting the bar get too far away from the body's center. Slipped disk for sure. You really don't need a ton of weight. It's a great movement if done right.
I see people with hips too low trying to squat the weight up. I do them with my knees only bent enough to stay in lumbar extension.
Exactly, many people try to maintain some kind of maximal "upright" positioning when doing squats and deadlifts. This is a complete mistake, the angle of your torso relative to the ground is a function of your genetics, proper mechanics will dictate torso angle, you cannot control it.
I want the smallest waist possible, used to deadlift heavy weights, waist was much thicker, I don't do abdominal work for the same reason, the greatest feeling on earth comes from having a very small waist, not a blocky, thick, pregnant waist.