But there is no basis for that.
Backwards.. -- You have no basis for your claim that States can respect an establishment of religion, or prohibit the free exercise thereof; or abridge the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
Requiring that state officials swear to obey the Constitution does not change the wording of the 1st amendment from "Congress" to "States and Congress". It means state officials are sworn to abide by whatever restrictions the Constitution placed on them.
Correct. Some of those restrictions include that they shall make no laws respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
When you make a contract with another person, it can place obligations on one party that aren't required of the other.
True. - If there is a 'meeting of the minds'. Both parties must understand the contract.
And when both parties sign the contract or swear to it, it doesn't somehow oblige the first party to comply with the obligations of the second.
In our Constitutional contract, all parties understood Art VI. State/local officials [as well as Congress] were pledged to support ALL of our Constitutional liberties, including those later outlined in the 1st Amendment and all following Amendments.
Until we had documents like the Magna Carta, the English Bill of Rights, or the Constitution, governments were allowed to do as they please. Without the constitution, they could and did those things. Why do you think we have state constitutions? It's because there were some provisions in the US constitution that didn't apply to the states.
This is not a radical interpretation of the Constitution. Constitutional scholars agree. Here's how Wikipedia explains it:
"Originally, the Bill of Rights was not intended to apply to the states; for instance, some states in the early years of the nation officially established a religion. This interpretation of these Amendments remained until 1868, when the Fourteenth Amendment was passed..."
Now if you are allowed to establish a state religion, that would mean that the 1st amendment did not originally apply to the States.