A human fetus—much less a human embryo—is, in fact, not an organism. Wiki has a nice suymmary of the definition:
In biology and ecology, an organism (in Greek organon = instrument) is a living complex adaptive system of organs that influence each other in such a way that they function in some way as a stable whole.The key word is “stable”—neither an embryo, or a human fetus before a certain stage of development, is capable of functioning as a stable whole. The “mother + zygote” pair is an organism, but the zygote itself is emphatically not.
An organism is in a non-equilibrium thermodynamic state, maintaining a homeostatic internal environment, and a continuous input of energy is required to maintain this state.
Your core hypothesis is, therefore, not true. That doesn’t invalidate your conclusion, but it does rubbish your argument.