As far as the bifurcating of a worm and how both halves can continue to live, I would like to make a contribution to the discussion.

When a worm is cut in half, the non-atman containing half continues to show signs of life due to the nervous reflexes of electrical energy in the nervous system of the invalid half. But, because this half of the worm has all the prerequisites for sustaining life, a jivatama quickly finds this situation as being conducive and supportive of life and moves in to make this his body.

The Paramatma is an unlimited source of life and energy and as such is constantly emitting jivatmas much in the same way that a light bulb emits light particles or the Sun emits light particles. As such there is an endless supply of unlimited jivas seeking to take form in the material energy.

As the subjetive evolution of the soul is always in progress, there is always a jiva waiting in the wings to take his body in the evolutionary stage of a worm. As such, when a worm is cut in half, a jiva is placed in that body by the material energy under the supervision of the Paramatma, according to the laws of nature governing the worm species.

This is the best explanation I can find according to the general principles of subjective evolution and the laws of material nature as they are carried out under the supervision of Paramatma.

I don't like to see these complicated questions go unanswered properly when a sincerely curious person wants answers.