Take a look at the What Makes a Good Tattoo thread in the General Tattoo Discussion part of the forum. Then go through the threads in Tattoo Advice. You'll find basically every answer you've asked for and more.
What boggles my mind is that this survey is for a dissertation AKA a doctoral degree level paper. I would hope that our university system has better research habits and Ph.D. cadidates.
Welcome, Jasmin. You'll fit right in here. The tattoos that you posted are amazing. Scott definitely is one of the nicest dudes. Also, glad to see a teacher here. A lot of bad seeds to keep in check here. just joking on that last part.
One rule that is often overlooked is when to do thick/thin lines in roman lettering. The thick line should always be on the downstroke when you start drawing the letter from the left-most point and draw the letter in the least amount of strokes possible.
I've seen a lot of very respectable tattooers "polish turds," so to say. I think that he was in the wrong to call you a disrespectful asshole, but I have seen it done, even on tattoos that were done by some of the old guard tattooers.