Let's distinguish between the geographical horizon line and geometrical horizon line. The geographical horizon is there because earth is a sphere, it is where sky and land meet. The geometrical horizon line exists because our eyes and cameras are projection devices, and it is where all vanishing points are located for our viewing direction. If we are looking horizontally (no pun intended), this geographical horizon is at eye level. Each direction has its own vanishing point, so a complex object with many directions, like an isokaeder, has many vanishing points.

Looks like the angle of mouth and eyes, i.e. almost frontal, doesn't match the angle of the head, i.e. three quarters.

Impossible, without knowing you.

When working out your lighting setup, it may help you to separate it from the drawing, that is to play with a light source to see how you can light your hand so its form in space shows up the way you like it. Shoot a reference, and then draw your hand using the reference.

Be aware man is no measuring device, so any measurement you take will have errors. There are two kinds of measuring. First there is sight sizing, where you work scale 1:1, putting things on paper the size you see them. Second, you have comparative measuring, where you compare sizes to one another as you see them, and on paper. Also, check out the proportional divider, which unites the two. Whatever you try, be prepared to make lots of mistakes aka to practice.

Put your drawing on top of your reference in your favorite software to spot the small errors that can totally destroy likeness. Do this not until you have done your very best to find this through construction and measuring, and a good night of sleep. Try to find out what went wrong, and how you can avoid your own personal pitfalls next time.

This is exactly like the choice of lenses in photography. You are free to pick a lens with wide angle and short focal distance, which offers you a broad view which emphasises perspective, or a lens with narrow angle and long focal distance, which brings things closer to you, at the cost of flattening things out.

Looking good! The door is a little wide, though.

I like it! I suggest you emphasize the main act of this composition, i.e. the robot-like character studying the doll head, by making everything else support this act, subduing whatever conflicts. For instance, Pinocchio's head in the top left is really nice, but it draws away my attention from the main act.

Check your proportions: the pelvis block should be a lot bigger. It refers to a big element which carries a good deal of your body weight!

You may want to start with a quick gesture, to layout what goes where, and then place your blocks? It helps to separate planning from execution.

There is nothing wrong with textures: respect your materials! I think it is funny how some try to get rid of textures in natural media, while digital artists do their best to get texture, simulating natural media.

I reshuffled the values a bit, to get rid of accidental deep shadows, like under her right arm, and make her fit the 5 value palette a little better. Feel free to shoot!

I support Sonja Müller's suggestion to do color studies. In addition, pick up some color theory. Some suggestions are http://www.huevaluechroma.com, http://handprint.com/HP/WCL/wcolor.html Definitely study Johannes Itten's seven colour contrasts.

A drawing is worthy of feedback if you do not know how to improve it yourself. Give it your best shot, give it a good night of sleep, fix the problems you can, and then ask somebody else for feedback.

Looking good, in addition to using more of a value range, I suggest you vary your lines for a more interesting piece, for instance using soft lines for soft hair.

Good work! Please be aware that the rib cage fits a 2x2x1 box, while the pelvis fits a 1.5x2x1 box (check out https://www.youtube.com/watch?v=uJMoplyGboI). Your pelvis is not high enough, by far!

The web already is a huge sketchdump, who needs more?

I kind of struggle with this too. I can be very hard on myself. Something that helps me when I get frustrated is looking at my old drawings to see how much progress I've made. Either that or taking a break and doing something that takes my mind off drawing even just for a little while. Hope this helps!

There is a lot to like about this, but you could have been more adventurous in choosing your colours. Try to add some cool colours?