How much do you weigh and how tall are you, as this plays a major role in how big they appear. Mine are 17 1/4 " at 210 but don't look it because I am 6'1" and have very long arms and muscle bellies, LOL.
This is SO TRUE! I'm 5'6" with "small" joints. This last summer I was able to meet up with one of the vets from the boards back east (business trip). I was dieting pretty hard then and weighed 175-178 lbs and was relatively lean - ~6% BF. He thought my biceps were 20"!!!! But they were only 17-1/2" (now they're "almost" 18").
Not sure the best way to explain how deadlifts helps build biceps - they help in both back and bicep development.
I have bad shoulders as well. I was taught bench press technique from a bro that holds state bench press records in several classes. He told me TO STAY AWAY FROM HEAVY DB presses. They're just an accident waiting to happen. He owns several gyms and has seen more people get injured from heavy DB work. I would say this is not the case if you have 4 good spotters when doing heavy DBs - but how often does that happen?!?