Casey,
Overall
The images are too soft looking and don't have a good range of tones. I would not be shooting with such a wide aperture when you are so close to your subject using this 50mm lens. It creates too soft a look for portraits. f/4 or f/5.6 would be better. A higher shutter speed would have been better to eliminate camera shake or put it on a tripod. I would bump your ISO up to 800 or so if you can't get more light on your subject.
#1 I don't like the fingers under the head. They are disconnected from the body and look out of place. Retouch the cloth to cover the fingers. I would also crop closer. The body goes on and doesn't have a good end.
#2 The eyes are too close to the edge of the frame to be looking off the page. The eyes need to be more centered overall to pull off this pose. I don't like the leg rising up on the right. The eyes have no highlights in them and have no life in them.
#3 Best image in my opinion but some work needs to be done on the skin to smooth it out. Notice how the fingers under the face in this image is connected to the body, this is better than #1.
#4 This image is just painful for me to look at. The body is all contorted and looks like it is twisted up