MDD,
You said,
“it says in the parsha of arayos:”velo sikarvu legalos erva…”.”
Right but isn’t that talking about the Aryaos mentioned in “the Parsha of aryaos”? I dont think Niddah is one of them.
Furthermore I don’t think that anyone argues that the “Harchakos” (like not touching eachother) that a married couple observes are only D’robonnon.
Why would not touching a niddah you are not married too be an issur Doraisa- not to mention “Yahrog va’al yaavor”?