On your page, you state that there is an opinion that qriat shma' is d'rabbanan: "There is a difference of opinion as to whether the obligation is from the Torah or mid'Rabanan." could you please cite the source, and the opinion? thanks.
The Gemara later (21a) records the opinion of Rav Yehudah, that Keri'as Shema is only mid'Rabanan. Tosfos (ibid. DH Hahu) adds that according to Rav Yehudah, the verse of b'Shachbecha is only an Asmachta. (This may be why the Gemara suggests its second answer to the order of "night-day" on Daf 2a.)
Halachically, most Rishonim, and Poskim (OC 61) reject this approach. However there are those who accept it, notably Tosfos (as can be seen from the places Rebbi Akiva Eiger points us to on Daf 21a), the Tosfos Rosh and Rebbi Yehudah Chasid (ibid.).
According to Sha'agas Aryeh (#1, based on Talmidei Rabeinu Yonah), even Rav Yehudah may agree that there is a biblical injunction to read something from the Torah every morning and evening. Exactly what to read is left up to the individual. (Tosfos does not seem to accept this approach.)
Gmar Chasimah Tovah,