So the spirit which came in the flesh as Jesus, is the same spirit that came in the flesh as David.
Jesus may have breathed His very breath into all of us, but that doesn't make us all Jesus. It sounds like you're saying that David and Jesus are one and the same but in different flesh bodies??? If you are, then that can't be true for Jesus is sinless while David was not.

God bless you

O my Jesus,
forgive us our sins,
save us from the fire of hell,
lead all souls to heaven,
especially those who are in most need of Thy mercy.
~ Fatima Prayer