Sorry, just don’t have time to annotate it but looking at the back of your head, the distance between C0 (head) and C1 (neck) and also C2 for that matter looks too far apart. In effect, it’s stretching up the back of your head and tilting your head forwards and possibly affecting your brainstem. The vertex you mention is what would normally be the top back of your head, if it was in it’s normal position.