3) In truth, your words have begun with foolishness and evil folly. How can I fill my heart with seeking and investigating, etc.? Why not? On the contrary, the opposite is logical (since it is said to serve this entity, which is created, it is appropriate to have a sincere heart. See Yosher Levav, page 3b, and strength to God).
We have an absolute obligation upon us and upon every individual in Israel to know the Lord, who is the Creator and not created, and to serve Him, as it is written, "Know this day and take to your heart that the Lord is God" (Deuteronomy 4:39). And it is said, "Know the God of your fathers and serve Him" (1 Chronicles 28:9). The sages permitted discussing matters of Torah even in places like the bathroom and bathhouse, where it is generally prohibited to engage in Torah thoughts.
However, they prohibited discussing matters of Torah in an inappropriate manner. As for your wonderment, how could they permit it? It is not surprising. And it is not preferable to follow the later Kabbalistic sects who deviated after the teachings of the philosopher, the author of the Zohar, who misled them regarding Rabbi Shimon Bar Yochai and his son Rabbi Elazar and their colleagues from the Great Sanhedrin who sat in the Chamber of Hewn Stone.
Regarding them, the Scripture says, "If a matter arises that is too difficult for you to judge, etc., then you shall arise and go up to the place which the Lord your God chooses, etc., and you shall do according to the word that they tell you, etc." Despite all of this, the Torah states that if the Great Sanhedrin unintentionally errs in a ruling, and the people act according to their instructions, they are required to bring a sacrifice for their unintentional transgression.
If their error involves idolatry, they are to bring a bull for a burnt offering and a goat for a sin offering from each tribe. And this is what is stated in Parashat Shelach: "But if the whole congregation of Israel sins unintentionally, and the matter is hidden from the eyes of the assembly..." (Numbers 15:26). And concerning other deliberate transgressions, if they err and it is hidden from them, they are to bring a bull for a sin offering from each tribe, as stated in Parashat Vayikra (Leviticus).
However, if the entire congregation of Israel unintentionally sins and the matter is hidden from the eyes of the assembly... (Numbers 15:25).