This particular narration is not that strong. There exists a difference of opinion between different Hadith Scholars on the authenticity of this narration. For instance, Albani calls is Sahih but Zubair ali Zai calls it Weak and instead writes:
إسناده ضعيف
سليمان بن معاذ ضعيف (د 1671) وحديث البخاري (5212) و مسلم (1463) يغني عنه
“Its chain of transmission is weak. Sulayman ibn Mu’adh is weak (d. 1671), and the hadith of al-Bukhari (5212) and Muslim (1463) suffices”.
(NOTE: There is one other narration in Abu Daud with more or less similar wording which is categorized Hassan by Hadith Scholars: https://sunnah.com/abudawud:2135. The comments below will address this hadith as well).
And the Narrations accepted by Bukhari and Muslim do not mention this particular point regarrding fear of divorce:
https://sunnah.com/bukhari:5212
https://sunnah.com/muslim:1463a
When we read the narrations of Bukhari and Muslim, we get an idea that Sawdah (rta) sacrificed her day out of her own will because of her old age, on her own and not because of the fear of divorce. There is no mention in any of such ahadith that Prophet (sws) expressed any such intention. Additionally, Quran 33:52 puts a bar on the Prophet (sws) to divorce any of his wives. In the presence of such clear Quranic directive, one should not speculate on the basis of doubtful narrations
As for the Quranic verse 4:128 being revealed on this occasion, a simple reading of verse 127 makes it clear that this is not the context of the verse 128. You can read complete context at the below link:
https://www.javedahmedghamidi.org/#!/quran?chapter=4¶graph=64&type=Ghamidi
Please also note that when it comes to the narrations on Shan-e-Nazul, there are always conflicting reports and we cannot rely on any one report when faced with such contradictions. It is the coherence, context and words of Quranic verses which decide their meaning, not the isolated reports on Shan-e-Nazul. As for this particular verse 128, again there are different reports on reason for its revelation. In the hadith of Abu-Dawood:2135 that I shared above, if correctly reported, Asiha (rta) herself mentions that this verse was either revealed on this occasion or for general scenarios. The narrator is not certain about this himself/herself. Similarly, Bukhari narrates a generic scenario from Aisha (rta) as a reason for revelation of this verse. See the two narrations below:
https://sunnah.com/bukhari:5206
https://sunnah.com/bukhari:4601
Therefore, it cannot be authoritatively asserted that the verse was specifically revealed about the issue of Sawdah (rta).