3. Why should the armpit be a source of strength? Easy to answer for some living at high latitudes: When your fingers get numb from the cold it is easy to warm them under your arms, where they quickly will recover by the warmth generated from the armpits.

Why should the world mountain (Mount Meru) be formed like an hour-glass? In Hamlet’s Mill it is hinted that the form is based on 'The internal motion of the cosmic tree':

This is a picture from North-West Africa: 'In the firmanent that motion marks the rotation of the stars above the earth and below the earth, around the fixed poles indicated by the axis formed by the elements in the middle of the cosmic tree.'

But there is not enough reason to connect the drawing and the idea of the hour-glass form for the world mountain to the 26,000 year long cycle of the precession of the equinoxes. I think it is more reasonable to see the drawing as a description of what happens in a single year, when the sky roof appears to revolve in this type of movement.

Moreover, if the world mountain is a description of Mother Earth hiding Sun and the stars during the night (and also during the night which is the dark winter season), then the hour-glass form will emerge, because in the tropics there is a steady light in contrast to the situation at higher latitudes. The 'dark cloth' will become greater and greater in proportion to how far away you go from the equatorial belt. And the effect is observed both in the far north and in the far south. In the tropics, however, the picture is the 'Chinese Mill':

The different explanations of the idea of Mount Meru reinforce each other, like the strands in a rope.