Got anything on the mechanics of suspending the crown, since obviously there's nothing above the head physiologically to hold it up?
Yes. I've explained before in previous threads that it is anatomically and physically impossible for a human being to elongate his head/neck along the longitudinal axis. Therefore, from a purely technical point point of view, the classic admonition to 'raise the crown' is based on a proposition that is false. We also know that anatomy/physiology/physics/biomechanics, etc. have come a very long way since the days when a series of mostly illiterate and uneducated laymen who happened to practice the societally lower class practice of martial arts first came up with their various sayings, admonitions and axioms. However, strict technical accuracy isn't absolutely essential when we take these sayings as the analogies and metaphors that they were always understood to be. In this case, the feeling (kinesthetically and proprioceptively) is such that it feels very much like one's head is stretched and suspended along the longitudinal axis of the body, even if it isn't.
What's actually happening here is that the head is brought into parallel with the transverse plane of the body, and very slight contractions of the erector spinae and trapezius straighten the spine to its full natural length. Similarly barely perceptible contractions of the latissimus dorsi, infraspinatus, rhomboids and deltoids serve to pull downward on the shoulder/pectoral girdle, with the resulting pull on the scapula and clavicle producing a very slight stretch of the trapezius, resulting in a feeling of the head stretching away from the body.
As to lowering the pelvis, the spine has a natural 'S' curve to it under normal healthy circumstances. Pronation of the lower spine does actually stretch that 'S', resulting in very slight elongation of the torso while the pronation is held.
As to your final point, I'm not exactly sure what it is you are subjectively describing, though I would suggest that "fulcrum" might not be the right word, given that there is nothing against which the cervical spine/skull can "anchor" in a real sense, though it's possible the feeling you are experiencing might very well seem that way. The multifidi and rotatores, along with other smaller supportive spinal muscles, can provide an impressive degree of spinal stability and even torsion (if carefully trained), which might have something to do with your experience.
