Halakah from God? Eating Ordinary Food in Purity?

In my latest reading of E.P. Sanders' Jewish Law from Jesus to the Mishnah, Sanders did two things.

1. Sanders asks a question on page 104: "Did anyone think that halakah was divine and as binding as the biblical law?"  He answers in the negative, and he focuses on the Mishnah and the Tosefta to argue that the treatment of the Torah was stricter than the treatment of the halakah and the words of the scribes.  According to Sanders, while it was believed that some traditions went back to Moses, there did not appear to be a belief that the entire oral Torah went back to Moses, at least not from the time of Jesus to the Mishnah.  My impression is that such a notion came later, as even the discussions in academies were eventually considered to have been revealed to Moses on Mount Sinai.

Although Sanders argues against Jacob Neusner, I think that there are elements of Neusner's work that overlap with Sanders on this issue.  Neusner argues that there was a time when the authority of the Mishnah was not self-evident to everyone, and so the Sifra sought to tie the commands and rulings of the Mishnah to the Torah, which was accepted as authoritative.  But that was one approach, according to Neusner.  Another approach was what is in Avoth: to say that the oral Torah was revealed on Mount Sinai.  (UPDATE: Actually, Avoth just mentions Torah, but many take that to mean the oral Torah.  Regarding Neusner's view on Torah in Avoth, I'm writing based on my vague recollection.)  Sanders and Neusner appear to agree that, in the Tannaitic period, it was not always believed that the halakah was revealed by God to Moses.

(UPDATE: Sanders and Neusner actually disagree on Avoth.  Neusner dates it to the mid-third century, whereas Sanders believes that it contains earlier material.  Sanders also appears to believe that it's ambiguous in Avoth what the Torah was that was revealed on Sinai and passed down----whether it's legends, teaching in its broad sense, Pharisaic traditions, or Pharisaic interpretations of the written Torah.  Sanders does not think that we should conclude from Avoth that the Pharisees put their traditions on par with the written Torah.)

2.  Sanders does not agree with Jacob Neusner that the Pharisees believed that they had to eat food in a state of ritual purity, necessitating that they wash their hands before every meal.  I talked some about this debate in my post here.  In my latest reading, Sanders focuses on the Pentateuch in addressing the question of whether ordinary Israelites were required to eat ordinary food in a state of ritual purity.  His conclusion is that the priests were required to do so, but ordinary Israelites were not.  But Sanders states that, if "wet food...fell on the carcass of a swarming thing", Israelites could not eat that food (page 148).  For Sanders, that's the only case in the written Torah in which a law of ritual purity is applied to ordinary, non-consecrated food that was eaten by ordinary (non-priestly and non-Levitical) Israelites.

Sanders makes an interesting point on page 148, though.  He notes that, according to Leviticus 17:3-5, Israelites only ate consecrated meat, since all meat had to be slaughtered at the sanctuary, presented as a peace offering, and thus "eaten in purity (Lev. 7.19-21)."  But Deuteronomy says the opposite, Sanders states: Because Israel's land was expanded, Israelites no longer had to have their meat slaughtered at the sanctuary, and people could slaughter meat in their own locations and even eat it in a state of ritual impurity.  Sanders also says that, in the first century, Leviticus 17:3-5 was "a dead letter" and was "dismissed in the Mishnah (Zebahim 14.1-2)."