/ic/ - Artwork/Critique

Superbeg here, It's not been a long while since I've seriously started doing the drawing on the daily and pretty much the 1st time I post on /ic/, I'm sorry if I'm going to ask something that's been answered 1000 times before.

Drawing I and II is me trying to copy a reference without making any change. Drawing III is me giving a shot at a simple pose out of my mind.
As it's probably apparent, I'm bad at building up the boxy skeleton of a character out of my mind/figure drawing, expecially if the limbs are moving backwards or towards the camera.

And while I'm reading "prospective made easy" on the side, I find it really hard to apply the whole "draw a railway going in the distance" with the human figure.
I understand that once you can draw a box tilted backwards you can then draw an arm inside that box, but it matters little if the box is the wrong lenght/size. (wich I think it shows, for example, in the arms and legs lenght of the III drawing, being too stubby).
>Am I begging/asking stuff too quickly and should I just stick to drawing more shape skeletons and boxes?

Bonus: Beside the obvious "Hands/feet" (wich I haven't take time to study yet, so it makes sense I'm bad at it.) any immediate problems i should fix before getitng bad habits?
I couldn't fit the references but filename.

inb4: "the bad habit is drawing anime".