The operative part, IMHO, is this:
8. Does God perform a new act of ex nihilo creation every time a human is born? Every puppy? Every seed that germinates? Every microbe that undergoes mitosis?
Indeed, the physical body seems first relevant to me in Gods covering Adam and Eves shame with coats made of skins:
Unto Adam also and to his wife did the LORD God make coats of skins, and clothed them. Genesis 3:21
And almost all things are by the law purged with blood; and without shedding of blood is no remission. Hebrews 9:22
Concerning the spiritual body, Jewish mystics point to the Hebrew words nephesh, neshama and ruach in Scripture used to describe the soul/mind/spirit.
More specifically, nephesh is the ordinary soul which all living creatures have (Genesis 1) and is returned to the earth upon death.
And neshama as you pointed out, is the breath of God which Adam received in Genesis 2 whereby he became a living soul.
Further, according to the mystics, the ruach is the soul pivot whereby the man chooses to be Godly-minded (neshama) or earthly-minded (nephesh.) That choosing parallels Romans 8.
And I knew him not: but he that sent me to baptize with water, the same said unto me, Upon whom thou shalt see the Spirit descending, and remaining on him, the same is he which baptizeth with the Holy Ghost. John 1:33
In that view, everything returns to the earth at death and new epiphenomenons begin at birth or conception.
But the Scripture speaks of creation being mindful:
Conversely then, the living souls which have ruach (choice) and/or neshama (breath of God) would "phase shift" (if P.S. Wesson is right) and continue onwards "in" the creation past the death of the physical body.
Moreover, we creatures called Christian being indwelled by ruach Elohim already exist "beyond" anything physical at all (including a phase shift):
But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his. - Romans 8:1-9
What? know ye not that your body is the temple of the Holy Ghost [which is] in you, which ye have of God, and ye are not your own? - I Corinthians 6:19
God's Name is I AM.
As usual, what God has provided through you is both enlightening and a true blessing!!
I perceive that we are, (again, as usual) on converging courses... :-)
I AM is still in control!!