I think these look really decent! They look like really lively poses and I love that that vibe comes through. It feels to me like you don't have a lot of faith in your measuring methods?
When I'm unsure of how big or small something should be (as it's a little closer or further away from me), I look at its size in relation to the body behind it. For instance, when a hand is outstretched in my direction, it could suddenly be as big as the chest. For outstretched limbs, when I can't easily compare its size to specific parts of the torso, I like to imagine horizontal/vertical lines starting from the wrist (or ankles) and going back towards the main section of the body. This helps me gauge how exactly far out an arm or leg is stretching.
There's a lot of other methods like these. I think the main concept is to let go of your 3-dimensional knowledge for a brief second and evaluate the pose as a flat 2D image while you gauge your proportions. I think when you think of it like this, no matter how many approaches you come up with, you can be more sure of your measurements and proportions overall.
I like the shading on the hair. I think doing in this way, you are appreciating the hairstyle as a whole, so maybe that's why it doesn't seem to mesh so well with the style of the head overall. You have a lot of lines defining the planes of the face, so maybe it would help to use lines to define planes of the hair, too. I would pay special attention to the volume of the hair, as well as how the hair meets the head, focusing on key places like the hair line, the parts behind the ear, and the back of the head.
