There is nothing wrong with your deadlift. But you are underweight probably 40 pounds, and riding a bicycle how much and often? And you are squatting...
Not at all. You have been doing something to irritate the shoulder, and you don't know what it is. Or you have an osteophyte on your distal clavicle...
All heavy pulls that are heavy enough to be considered heavy pulls are done for one work set. If they are heavy enough, the low back in the last rep...