A non-frum relative asked me an interesting question based on some aspects of halacha I was trying to explain in other matters. The Torah prohibits a couple from having relations before she has gone to the mikveh. The relative asked: Is there a difference between the time of bleeding and when "sheva nekiim" in terms of the nature of the issur? And second, if the issur of the Torah is on bi’ah, does that mean that any other sexual contact between them is an issur derabbanan, or would abstaining from any other sexual contact besides bi’ah simply be considered a "chumra"?
ב"ה Shalom From the practical point of you, the nature of the issur of a woman remaining in her Nidah status does not change until she has gone to the mikveh and as known there are other stages along the way,among them the "Shivah Nekiim" as you mentioned, before going to the Mikveh. In regard to abstaining from any other sexual contact besides "bi'ah, IN NO WAY is this to be considered a "chumra". It is an essential part of the prohibition. According to the Rambam (מצוות לא תעשה שנ"ג) , any physical contact between a man and his wife who is a niddah is an ISSUR of the TORAH. This was also the opinion of the Rishon Lezion, Rav Mordechai Eliyahu zt"l.(,פרק ה, דרכי טהרה ) Also, the other prohibitions such as handing her things are issurim derabbanan = Rabbinical prohibitions, due to the severity of the laws of Niddah in order to safeguard the physical abstinence. These are not Chumras. All the Best