HI Kimberly,
Yes, yes, they are all correct! Until you get your new lens
there are a couple of things you might try.
When you photograph your subject, get at least one image with , for example the hands, that shows the hands on roughly the same picture plane as the body. With that information you can make relative measurements about the size of the hands ( in this example) compared to the size of the head. Then you would just make an adjustment in that measurement when you paint the hands. This adjustment can be a good approximator but I think it's always best to be WAY back and zoom in.
The other thing you might play with if you have Photoshop skill, is to try using the spherize function. It's located under Filter - Distort- Spherize. I haven't personally used it , just know that it's there. I have Photoshop CS so I am not sure whether other versions offer Spherize.
Good luck, I just LOVE that first image!