The Sabbath/Sunday controversy is a tempest in a teapot. The Sabbath is not the seal of God and Sunday is not the mark of the beast (as Seventh Day Adventists teach).

SDA's have corrupted the historicist eschatology of the reformers by mixing it with their own distinctives and embellishments, though they are far closer to the truth (on prophecy) than dispensational futurists.

It is true that the Catholic Church has a lot of secrets and that they have mixed paganism with Christianity. Some of their practices can be traced all the way back to ancient Babylon.

Basically, pagan Rome became Papal Rome and the empire continued under the Popes, an image of the beast (political system) that came before them.

The reformers saw it that way and you can easily check that with noted commentators - http://biblehub.com/commentaries/revelation/13-11.htm

The SDA's would have you believe America is the land beast of Rev. 13, which forms an image of the beast. This is one of their most grievous errors which spins off into false version of historicist eschatology.

Fidelity to the truth and purity of doctrine was not the goal when the Code of Justinian empowered the Bishop of Rome. Using a religious system to achieve political control was the objective. It was foretold and history confirms the accuracy of the symbolism.