It's the heartbeat that matters. Heartbeat is something a living thing does.
A girl can be brain dead and in a coma, but until her heart stops beating, she isn't dead.
Also, you are using religion as a political tool (for the left), throwing around the Ten Commandments, like you understand things. If there is a heartbeat, and you stop it, it's muder. You yourself said no exceptions.
Prevention, not abortion, is key. But you're rationali that non-sentient life is not valuable. Planarians don't have a working brain. But they do quite well for themselves, reproducing even when cut apart. A brain is not necessary for life. Neither starfish nor plants have a brain, but burning a forest down would be a crime.