I'd say that you don't approach the question with the sophistication it deserves. The principal that the whole of the creation was to worship the God of Israel (and yes, worship is primarily about hearing the Word and believing) has never been in question. Luther talked about the Tree of the Knowledge of Good and Evil being given for just this reason. So again, there is a universal principal here that any careful and concerned reader of the O.T. immediately discerns.
Ah! It's not really the Law (or even the Decalogue) that you are talking about, but the "principals" behind them. I don't see them as equivalent.
I do not believe that the oldest forms of the sabbath laws were about worshiping God (or that principal). They were simply about resting and taking time to refresh - people, land, and animals.
Exodus 23:10-11: For six years you shall sow your land and gather in its yield; but the seventh year you shall let it rest and lie fallow, so that the poor of your people may eat; and what they leave the wild animals may eat. You shall do the same with your vineyard, and with your olive orchard.
Exodus 23:12: Six days you shall do your work, but on the seventh day you shall rest, so that your ox and your donkey may have relief, and your homeborn slave and the resident alien may be refreshed.
Exodus 34:21: Six days you shall work, but on the seventh day you shall rest; even in plowing time and in harvest time you shall rest.
In my opinion, the desire to separate the 613 commands into moral, civil, and ceremonial, is our human attempt to decide which laws (especially if they are the will of God) no longer apply to us. In other words, we look at the commands and decide, "This command makes sense to us now, so we'll call it 'a moral law'."