Actually the ninth commandment is not about lying. It is speaking about bearing false witness and has in mind a court of justice.
As you yourself made clear deceit is an integral part of warfare, and indeed it is of salesmanship. Most advertising is deceitful to a certain extent. Many Chinese Christians would willingly lie in order to 'save a person's face' and see themselves as justified in doing so. Thus lying is a more complicated issue than merely bearing false witness, and it is sometimes justifiable as you admit. If I had been in Nazi Germany hiding a Jew I would not have considered it reprehensible to lie in order to keep him hidden.
So using your criteria lying might get me to Heaven

Is my eternal destiny therefore dependent on my being able to discern when deceit is right and when it is not?
Your problem Jason is that you are trying to save yourself. What if your interpretation of deceit happens to be wrong? Then you will go to Hell when you thought you were bound for Heaven. It is so different for us who are in Christ. We are being borne there by Another. Whilst He may sometimes have to give us a good thrashing He promises to see us safely through, covering us with His righteousness. Thus we are safe in His hands.