Caveat: I personally did not train following Hampton, so I am not familiar with the exact details of his method.
First observation: You are obviously already applying a lot of thoughts and critiques to your own drawings. This is great. (I should maybe do that a bit more myself)
Your lines look purposeful and clean, that is always good.
About your construction method,... I don't know how Hampton does it, but I personally found that my construction of the human form made good progress, once I found a good abstraction of the ribcage and pelvis first, and then the placement of the joints as a next step. I see you are using the pelvis, but so far you don't include an indication of the ribcage. Instead you mention the spine.
I guess the logic of focusing on the spine is to make it easier to progress from an initial line of action. I am a big fan of indicating ribcage and pelvis first.
a) Ribcage isn't a very complex geometrical form to incorporate: more or less a flattened upright egg, with the underside cut off along the lower ribs.
b) The ribcage pretty much defines the center third of the spine anyways, so finding the ribcage already answers a lot of questions. Add shoulder joints, head, and tissue (muscles, breasts, body fat, as needed), and you are already done with the construction of the upper body.
1