Shem being the son of Noah had to create a Beit Din, one of the seven
Noahide concepts. The purpose of this Beit Din was to decide disputes and
create legislation for the proper governing of society. Ostensibly Yaakov
had a shimush, apprenticeship in the yeshiva and learned how to be a judge
Shem is refered to as having prophesy (see rashi in Parshat Toldot) and at
the least having Ruach Hakodesh in deciding and promulgating laws.
As to the general question of the Avot learning Torah SHebeal Peh, I would
look (once again) in Toldot, I believe it is in Bereshit chapter 26, either
verses 4,5, or 6. There Rashi quotes the gemorah in yevamot and the midrash
rabah as to the concept of the Avot following Torah SHebichtav and SHeBeal
As to whether the Avot wore tefillin, that is a question as to how you view
midrash. Is it literal or a drush with a message being the point of emphasis.
As to why we don't follow the decisions of Shem V'Ever as opposed to the
discussions of SHamai and Hillel:The Torah that we follow was given to
Moshe and Bnei Yisrael at Har Sinai. It wasn't logically derived as was
much of what Shem V'Ever decided. At Sinai we were Mushba Umeumad, sworn to
oath to uphold the Torah. The Avot were not sworn to uphold the Torah (that
is why it is a special merit for them). Hillel and SHamai and all
discussions in the Torah Shebeal Peh are towards that end. To fulfill the
oath of upholding the Torah
I hope this has been of some help.