I also used a 3ds to draw all of my digital art too, so you're not alone in that boat. ^^"
Whaaaaaat?? Oml I is very ashamed at myself
Yeah it's like that. I always focus on the head a lot more than the body, that's why I usually do shoulders-up.not sure with prices.
for rating, your body proportions for the full body example looks pretty good but the head seems a bit big in all of your examples. Unless that was your main focus when drawing them (the focus to be on the head).
are you opening a shop? try a pwyw first, add the prices up all together, divide the amount of people, and there is the demand for your art. I would wait until over 30ish people to do all this calculation so you have a big sample size to work with. It would be better if you had more than that because, it's pretty self-explanatory.