That rule, in particular, means nothing if it wasn't given by God, does it? Why should I care what I do on Saturday (or Sunday), if there is no God, and all of this is just some "fictionalized account" that teaches us some truth.
(The New Testament permits worship on Resurrection Day...Sunday. Also, Jesus pointed out that most of the little legalisms that were practiced on the Sabbath were entirely unnecessary. The Sabbath was supposed to be renewing and refreshing for humans -- not a pain in the ass.)
Keeping the Sabbath holy is one of the commandments. It has nothing to do with worship -- one can worship seven days a week. The Sabbath (Saturday) was to be a day without work which was devoted to God and family. Jesus, who you claim to follow, said he did not come to change the law, which means the law is still in effect (IOW, Sunday does not replace Saturday).
So, do you keep Saturday holy?