>he asks me which verse defines these two covenants and which verse distignushes moral law vs ceremonial
>use historical examples, argue by extension since dietary laws, sacrifice laws and circumcision are fulfilled we can deduce that all these "ceremonial/sacrificial laws" are fulfilled including mixed fabrics meant to separate israelites…
Your fault really, this whole moral/civil/ceremonial law distinction is a complete myth. You are in fact not under ANY of the laws of Moses moral or otherwise. You failed to convince him because you didn't know this basic fact.
The atheist was right, there is absolutely nothing which distinguishes moral from ceremonial in the law of Moses in the bible, in fact the law of Moses itself states that you have to follow every law within the law of Moses (Deut 6:25; 27:10; 28:58) - is that a moral or ceremonial command? We have this repeated for us in our New Testaments (James 2:10).
I strongly, strongly recommend that you read and meditate on the epistle to the Galatians which concerns this issue.
You basically needed to show him what the end of Galatians 5 summarises - that we are not under the law, but we are not lawless people. When a Christian decides not to murder, or steal or commit sodomy, it absolutely should not be because he is living by a stripped down version of the law of Moses.
"But I say, walk by the Spirit, and you won't fulfill the lust of the flesh. For the flesh lusts against the Spirit, and the Spirit against the flesh; and these are contrary to one another, that you may not do the things that you desire. >>>>But if you are led by the Spirit, you are not under the law<<<<. Now the works of the flesh are obvious, which are: adultery, sexual immorality, uncleanness, lustfulness, idolatry, sorcery, hatred, strife, jealousies, outbursts of anger, rivalries, divisions, heresies, envyings, murders, drunkenness, orgies, and things like these; of which I forewarn you, even as I also forewarned you, that those who practice such things will not inherit the Kingdom of God. But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faith, gentleness, and self-control. Against such things there is no law. Those who belong to Christ have crucified the flesh with its passions and lusts."