I agree with that, but the terms "Old Covenant" and "Ten Commandments" cannot possibly be synonymous, or we'd be able to use them interchangeably, which Romans 3:31 will not allow because we Christians do not "establish the Law Old Covenant".
The Old Covenant was abolished, but the components of it - the Law and Promises - are preserved in the New Covenant, but with better promises because they are no longer ours but God's promises.
Therefore, I agree 100% with you that the Old Covenant is passed away, but neither God's promises nor His Ten Commandments have passed, as evidenced by Psalms 111:7-8......and WADR your arguments have not harmonized that verse and I have to respectfully say until that verse no longer contradicts your conclusion --- that the law which God wrote with His own hands has expired --- I must urge you to revisit the issue until Psalms 111:7-8 does not contradict your findings. Peace.
The Ten Commandments were the Old Covenant. Consider the following;
“And He (God) wrote upon the tables the words of the covenant, the Ten Commandments.” Exodus 34:28
“And He declared unto you His covenant, which He commanded you to perform, even the Ten Commandments.” Deuteronomy 4:13:
“When I was gone up into the mount to receive the tables of stone, even the tables of the covenant.” Deuteronomy 9:9:
“So I turned and came down from the mount . . . and the two tables of the covenant were in my two hands.” Deuteronomy 9:15:
“There was nothing in the ark save the two tables of stone which Moses put there at Horeb, when Jehovah made a covenant with the children of Israel, when they came out of the land of Egypt,” I Kings 8:9
“And there have I set a place for the ark, wherein is the covenant of Jehovah, which he made with our fathers, when he brought them out of the land of Egypt.” I Kings 8:21
The second of these two texts is repeated in II Chronicles 6:11.
Consider “The ark of the covenant” that held the Ten Commandments (Numbers 10:33; Jeremiah 3:16, and other places)
Also; “It contained the golden altar of incense and the ark of the covenant covered entirely with gold. In this ark were the golden urn containing the manna, Aaron’s rod that budded, and the stone tablets of the covenant.” (Hebrews 9:4) (NET)