Murder is a legal term and depends on our legal definition. We don't legally define abortion as murder. We could, but we don't. You'd be better off saying that abortion is the killing of a human being, and that human being doesn't deserve to be killed. Which is a fine argument.
If the mother chooses not to donate to the fetus/embryo, and the fetus/embryo is removed from the womb before viability, that fetus/embryo is going to die. But it's an inevitable result of the mother cutting off donations to the fetus/embryo.
Even if that's the case, that doesn't prevent the mother from changing her mind and withdrawing consent later.
Now, I fully understand your points, and I sympathize. I don't oppose certain restrictions to abortion, but the donation argument is making it hard for me to oppose abortion.