Hi!
Difficult angle to work with I would say.
Judging from your fifth image, Your left forearm (including wrist) seems too elongated
and too rectilinear, actually it looks like a stick. As for the lightsource, I'm not sure if the left forearm should be that highlighted...
Strangely, your 1bit sketch, really looks more accurate than your coloured images.
Palette is fine, I like this combination of hues for human skin application.