What I've posted of your quote in red is the root of the error.
The Mt. Sinai Covenant was agreed upon BEFORE THE LAW WAS GIVEN. It was then ratified three days later with the giving of the law and shedding of blood.
The Law wasn't created by the covenant.
The Law wasn't the covenant.
The Law wasn't the covenant.
The covenant was the marriage agreement between two parties regarding obedience. The term of the agreement was to "obey God and be blessed". The Law existed outside of the covenant, immutable, eternal, and everpresent. In fact, The Law is The Word.
this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.