I had to collect many sources of information on head anadomy and muscles of facial expression. I´m hoping though that in the future Stan decides to make a nice course on it. the amount of information you may want to know is SO VAST though who knows if or when it will happen.

Very nice sweeping force in your lines, they are rather clean! I see what is holding you back from producing a 3D feel in your head construction. It is the fact that your lines are not agreeing with each other, they do not relate to one another in a singular 3D space. This is because when lines are parallel or converging, they tell our brain that they are part of a plain, like a wall, in a 3D reality that we are seeing through a sort of window, which is your picture plane, the paper. The illusion is thus broken because the lines do not agree and we can immediately then read them as flat linear shapes on a flat surface. To fix this you must study Perspective. There is no way around it but fortunately it is not at all rocket science, although it definitely has mathematical concepts in it, such as parallel lines, angles, etc. I will recommend that you check out a fun little video to introduce yourself to Perspective made by the wonderful Marshall Vandruff as a Halloween special on youtube: https://www.youtube.com/watch?v=eFKMw8YekFY Follow that by checking out a book called Perspective Made Easy, and patiently do the exercises. It might take a few weeks to get through it all, but it is THE most essential tool you will have as an artist that wants to draw things that appear to have volume.

Wow so clean, so pristine. I feel some Bridgman here hehe

Looking great! Now on to drawing the forms that are learned in your head while using photo reference to place the Pelvis where it goes. I found it super challenging to judge the tilt according to the pose, since the anatomical tilt is not there at all when sitting or when other motions are applied like leaning, but if the reference is good enough you will have a good time!

The deltoid tuberosity on the humerus should be about half way down the humerus, so yes, stan appears to have made the humerus a but shot there, about a third too short, but correct me if I´m wrong, since I´m going off the insertion of the Deltoid, which is half way down the humerus.

I see great effort, Arthur! How often do you practice? It's good to get in the habit of daily drawing to improve on the hardest things like line control and proportional accuracy with eye measuring. Also, try to take your pictures with clear even lighting so we can appreciate them better. Sunlight works great! Best of luck.

Nice! I also like making sheets with tonnes of useful notes. Don´t forget to go over them after a few weeks and see if you wanna make improved revised notes!