So if I understand you correct, your argument is that morality is equally valid with and without God? Meaning we wouldn't be able to tell the difference either way.
It is, of course and tthat is the reason why God requires his servants to obey the secular authorities, because they reflect his justice to a certain extent. Humans are "lineage" of God in the sense of our conscience and way of reasoning the world. But God is always the superior authority, because since He was the one who created us, he knows better than we ourselves what should be the way to treat each other, and what is good for us or not of all the things that could occur to us.
Let every person be in subjection to the superior authorities, for there is no authority except by God; the existing authorities stand placed in their relative positions by God. 2
Therefore, whoever opposes the authority has taken a stand against the arrangement of God; those who have taken a stand against it will bring judgment against themselves. 3
For those rulers are an object of fear, not to the good deed, but to the bad. Do you want to be free of fear of the authority? Keep doing good, and you will have praise from it; 4
for it is God’s minister to you for your good. But if you are doing what is bad, be in fear, for it is not without purpose that it bears the sword. It is God’s minister, an avenger to express wrath against the one practicing what is bad.
If human conventions are against the law of God, it is obvious that the superior is served. A child would like to eat candy all the time. The father knows what would happen if he let him.