Because Hashem Said So or Because Totty Said So?

In honor of the recent holiday of Shavuos and the current "holiday" of Father's Day, I'd like to share a beautiful vort connecting the two, based on the Yaavetz (Tzapichis BiDevash, Drasha al Chag HaShavuos)

The Gemara in Shabbos says:

שבת פ״ח א

״וַיִּתְיַצְּבוּ בְּתַחְתִּית הָהָר״, אָמַר רַב אַבְדִּימִי בַּר חָמָא בַּר חַסָּא: מְלַמֵּד שֶׁכָּפָה הַקָּדוֹשׁ בָּרוּךְ הוּא עֲלֵיהֶם אֶת הָהָר כְּגִיגִית, וְאָמַר לָהֶם: אִם אַתֶּם מְקַבְּלִים הַתּוֹרָה מוּטָב, וְאִם לָאו — שָׁם תְּהֵא קְבוּרַתְכֶם. אָמַר רַב אַחָא בַּר יַעֲקֹב: מִכָּאן מוֹדָעָא רַבָּה לְאוֹרָיְיתָא. אָמַר רָבָא: אַף עַל פִּי כֵן הֲדוּר קַבְּלוּהָ בִּימֵי אֲחַשְׁוֵרוֹשׁ, דִּכְתִיב: ״קִיְּמוּ וְקִבְּלוּ הַיְּהוּדִים״ — קִיְּימוּ מַה שֶּׁקִּיבְּלוּ כְּבָר.

Shabbat 88a

The Gemara cites additional homiletic interpretations on the topic of the revelation at Sinai. The Torah says, “And Moses brought forth the people out of the camp to meet God; and they stood at the lowermost part of the mount” (Exodus 19:17). Rabbi Avdimi bar Ḥama bar Ḥasa said: the Jewish people actually stood beneath the mountain, and the verse teaches that the Holy One, Blessed be He, overturned the mountain above the Jews like a tub, and said to them: If you accept the Torah, excellent, and if not, there will be your burial. Rav Aḥa bar Ya’akov said: From here there is a substantial caveat to the obligation to fulfill the Torah. The Jewish people can claim that they were coerced into accepting the Torah, and it is therefore not binding. Rava said: Even so, they again accepted it willingly in the time of Ahasuerus, as it is written: “The Jews ordained, and took upon them, and upon their seed, and upon all such as joined themselves unto them” (Esther 9:27), and he taught: The Jews ordained what they had already taken upon themselves through coercion at Sinai.

Question 1: The Yaavetz asks on this Gemara from a Gemara in Bava Basra which says:

בבא בתרא מ״ז ב

אָמַר רַב הוּנָא תַּלְיוּהוּ וְזַבֵּין זְבִינֵיהּ זְבִינֵי מַאי טַעְמָא כֹּל דִּמְזַבֵּין אִינִישׁ אִי לָאו דַּאֲנִיס לָא הֲוָה מְזַבֵּין וַאֲפִילּוּ הָכִי זְבִינֵיהּ זְבִינֵי

Bava Batra 47b

Rav Huna says: If one was suspended, e.g., from a tree, and thereby coerced to sell a certain item, and he sold it, his sale is valid. What is the reason? The Gemara suggests that it is because whatever a person sells, were it not for the fact that he is compelled by his need for money, he would not sell it, and even so, his sale is valid. This indicates that a transaction performed under duress is valid.

We see from here that an acquisition under duress is valid, if so how could the Gemara in Shabbos say that Klal Yisrael had the excuse that they were "forced"? Even if they were indeed forced, the acceptance would still be valid based on the law in Bava Basra?

Question 2: Rashi on this Gemara writes:

רש"י על שבת פ״ח א:ה׳

מודעא רבה - שאם יזמינם לדין למה לא קיימתם מה שקבלתם עליכם יש להם תשובה שקבלוה באונס:

Rashi on Shabbat 88a:5

"Large caveat" -that if they are called to judgment as to why they [the Jews] do not fulfill what they have accepted upon themselves, they are able to respond "Our acceptance was coerced [and therefore null"]

Yismach Moshe asks, why does Rashi write in a long-winded way "as to why they don't fulfill what they have accepted upon themselves"? Why didn't he write simply "as to why they don't fulfill the Torah"?

To answer these questions we need to clarify the "mechanics" of how the acceptance of those who were at Har Sinai effected a responsibility on their children and future generations.
The Meforshim say that the reason the children became subjugated to the Torah from the fathers' acceptance was by means of Kibbud Av, honoring ones father's wishes. If the father was keeping the Torah, the child, by way of respecting his father, needed to follow in his ways and also keep the Torah.
But it stands to reason, says Yaavetz, that if what the father is only fulfilling the Torah because he was forced to, the child is not obligated to follow in his ways, being that even his father isn't too thrilled about what he's doing.

With this we can understand the Gemara in Shabbos. Although the fathers were bound by the vow they made at Har Sinai, following the the Gemara in Bava Basra that a vow or sale under duress is effective, nevertheless, the effect of that vow didn't extend to the next generation since the acceptance was not done whole-heartedly.
Thus, the "excuse" the Gemara is referring to is not in reference to the fathers' acceptance, rather it is being said in regards to the children's acceptance, since they had a valid "excuse" as to why they don't need to keep the Torah, since the "Kibbud Av" mechanism did not bind them.

And this idea is possibly what Rashi is alluding to in his choice of words. Rashi is stressing that the excuse mentioned in the Gemara is said specifically in regards to the children to obviate themselves from what their fathers had "accepted upon themselves", and since their fathers' acceptance was forced, that acceptance should not extend to them.

Yaavetz adds, that although the excuse of the children would have obviated themselves from keeping the Torah out of respect of their fathers, they still would have been obligated to keep the Torah because of "dina d'malchusa dina", "the rule of the king is the rule", and since all of Klal Yisrael for all generations accepted Hashem as their king (he proves this at length), therefore the children would still practically need to obey the Torah.

Although according to this conclusion, there seems no difference as to why we would need to keep the Torah, either because of Kibbud Av or the King's rule, there is a difference in respect to how great the punishment would be for neglecting to listen to the Torah.
If were obligated because of respecting our fathers and because of the requirement to follow the King's rule, the punishment would be greater than if we were just obligated because we need to follow the King's rule and not out of respect for our fathers.

Based on the conclusion of the Gemara in Shabbos that we "re-accepted" the Torah in the days of Achashverosh, we are bound to keep the Torah for both reasons.