In the first, what I can only guess are scars don't really look like scars. If they are supposed to be, they need to blend into the skin a little more. The same with the collarbones. Just less outlining, I think might work better. And on the back, we should be able to see how it is raised on the profile.
The left side (his right) looks pretty close to what they should, actually.
His nose could use some more careful reworking down at the bottom, the general shape is a little off. It looks like a mix between and European and an African nose. It's going in the right direction, though.
I think the second one is pretty good, other than the sizing, which you seem to already know about. Her foot should probably be a little bigger as well. I think her back actually looks good, it would just be awkward to sit in that position. But it looks feasible.
In reality, we might not be able to see her ribs, especially with a little bit of a belly like she has. But I like the way it looks in the picture. It fits well with the colors. I think it looks a little eerie that way.
I think this third guy is the worst of the bunch. But I might just be comparing it with the more realistic styles you've used, especially in his face. His legs look kind of off. Like we are looking a little bit down on his legs, but the rest is straight on. And it look as if he has extra short thighs. That might be the cause of the former.
His wrist joints look a little wonky. It seems almost like the part under his pinky looks like the bulge under the thumb on the bottom side of the hand. I would expect it to look more bony.
Hand reference photos See how in the first one there's a bone under the pinky? This is totally nitpicky, though. I'd worry more about the legs for that one.
This last one I just adore. Her hand might be a little small, with quite thin fingers for being such a big woman, but I love everything else about it.
I do like your coloring and style. It looks good.