Lets assume for the sake of argument that you are right (legal scholars like Dr. Charles E. Rice have addressed this matter, the meanings of "born," "person", "nonperson", "human" with regard to the 14th amemdment indepth) and that unborn children are left out of the Constitution and the 14th amemdment. The Natural Law given to us by God and make know to us by reason still tells us that the unborn child is a person, a human being, thus with a right to life. Even if the constitution did not cover him (the same way the text was said not to cover slaves) murder could still never be endoresed or allowed under cover of law.
Sure it could, and is. Again, most states allow the use of deadly force against intruders. But there are enough cases out there of some innocent fool getting his head blown off by trying to enter the wrong house in the middle of the night drunk, etc. Shooting someone in such circumstances is murder by my understanding of the word, and the corner will classify the death as a homocide.
You are confusing morality and law. I agree that abortion should be illegal. In fact, it is illegal in most states, other than the fact that prosecutions for the crime will be thrown out under Roe vs. Wade. But we do ourselves no credit by exercising wishful thinking to create things int he law that are not there.