wa 3alaikumus-salam,
First of all, may Allah guide you and us to the truth, there is no such a thing as "for the sake of argument" with regards to 33:33. You said:
let's agree " Ayat tathir" was part of 28-34/35 and let's agree the wives were the ones being addressed.
Of course it is part it, it is ONE long verse, Shias cut out a PART of a SINGLE verse (the last bit) and TAKE IT completely out of context and present it as a verse (and even name it "Ayah Al-Tathir"), this is academic dishonesty of the highest order (please don't argue with the grammar argument, even more knowledgable Shias who are familiar with BASIC Arabic know why the suffix changes to KUM i.e. masculine plural, this is because AHL AL-BAYT is a MASCULINE noun, the head of the Ahl Al-Bayt is the HUSBAND i.e. the Prophet. Allah used it also for Ibrahim's wife!), one could call it one of the biggest cons in history.
One could also simply start a social experiment asking Shias about "Ayah Al-Tathir", no doubt the majority would believe that it is actually a single clear cut verse, not knowing that it is actually a PART of a longer single verse (all about wives!) mutiliated by Shia scholars who struggle to find a single clear cut verse in the Qur'an supporting their non-Islamic beliefs (like infallibility for the Ahl Al-Bayt).
Even Shia scholars like Ayatullat Haidari admit to the fact that the entire verse (and the verse before and after it!) is about the wives and that a basic rule in tafsir of the Qur'an is that each verse must be looked at and understood within its CONTEXT (misdaaq):
He bashes Shias for all their cheap arguments (and mentions verses from the Qur'an were OTHER wives of Prophets are addressed in with the MASCULINE SUFFIX of Ahl Al-Bayt i.e. the Sunni understand is a pure Qur'anic one), however, his bias and arrogance make him say that the ONLY leg Shias have to stand on are the HADITH about who the Ahl Al-Bayt are NOT the verse, but even the hadith he admits are refuted by Sunnis who ACKNOWLEDGE their authenticity (i.e. hadith Al-Kisa') but (rightfully) say hadith like hadith Al-Kisa' must be understood in the CONTEXT of the verse i.e. just because 'Ali and his family are INCLUDED in the verse doesn't mean we exclude the wives. The man is at least as honest as to admit that the Sunni stance is extremely strong. As for what he said about the narrations (as if hadith Al-Kisa' is in their favour, it's not), our brother Al-Hindi wrote one of the best articles available in English language regarding the Tathir and Kisa' shubhah of the Rafidah, literally every shubha is refuted in his articles:
https://youpuncturedtheark.wordpress.com/2010/11/22/does-verse-of-tatheer3333-makes-anyone-infallible/https://youpuncturedtheark.wordpress.com/2010/12/20/a-scientific-dialogue-regarding-incident-of-kisa-revealing-some-facts/https://youpuncturedtheark.wordpress.com/2010/10/09/for-whom-the-verse-of-purificationtatheer-was-revealed-and-what-is-the-concept-of-purification-let-the-quran-answer/https://youpuncturedtheark.wordpress.com/2010/10/07/ahlahlebayt-a-collective-noun-and-its-usage/https://youpuncturedtheark.wordpress.com/2010/10/06/quran-explicitly-shows-that-wives-of-prophetsaw-are-ahlebayt/https://youpuncturedtheark.wordpress.com/2010/10/06/usage-of-word-ahlahlebayt-in-quran/https://youpuncturedtheark.wordpress.com/2010/10/06/definition-of-%e2%80%9cahlel-bayt%e2%80%9d-from-linguistic-perspective/https://youpuncturedtheark.wordpress.com/2010/10/05/what-was-the-reason-for-the-purification-of-blessed-wives-of-prophetsaw/https://youpuncturedtheark.wordpress.com/2010/10/05/the-relation-between-verse-of-purification-and-divine-commands-before-it/https://youpuncturedtheark.wordpress.com/2010/10/05/detailed-explanation-of-verse-of-purificationayat-e-tatheer-3333/https://youpuncturedtheark.wordpress.com/2016/03/26/hadeeth-kisa-cloak-explained-by-an-ex-shia-scholar/# This will simply means that only those who fulfill those admonitions righteously and adhere to it from the day of revelation till the time of death will be purified.
# How does umm al-mu'minina Aisha (especially) fair in those conditions, during and after the demise of Nabi?
This verse doesn't speak about infallible super humans or semi-divine individuals, it addresses normal human beings, wives, Allah knows that no human being is absolutely perfect, all of us sin in one way or another, however the wives of our Prophet (unlike other Prophets) are of a very special status so Allah has burden them with a heavier burden than other females, as long as the females addressed in the verse do their admost to adhere to the conditions, then Allah will purify them. Allah revealed similar verses about the Prophet and his Sahaba:
8:11 [Remember how it was] when He caused inner calm to enfold you, as an assurance from Him, and sent down upon you water from the skies, so that He might PURIFY you thereby and free you from Satan's unclean whisperings and strengthen your hearts and thus make firm your steps.
No sane mind (although if Sunnis would exaggerate with the Sahaba as Shias do with Ahl Al-Bayt they would have done that, but Alhamdulillah Sunnis are on the middle path) would argue that the Sahaba are completely cleansed from the whisperings of Shaitan or that they don't sin. Same with verse 33:33, Allah revealed it about a group (wives in specific) that would sin in the future, Allah is All-Knowing, he was certainly aware of it, yet despite that (Him knowing that they are fallibles) he encouraged them to abide by the conditions. This means that sins committed by Hafsa, Maymunah, Umm Salamah, 'Aisha do not exclude her from the verse (especially not fitan like the Jamal war that was chaotic and 'Aisha till the end of her life - according to authentic narrations - regretted to have participated in the first place. Tawbah/repentance IS a sign of believers).
Also, many Sunni brothers say "your Imams were born pure and infallible, what's the point of purification?" I respond by:
# Why does Nabi continue to make istighfar more than 70X in a day despite according to your tafasir of sura fatih:1 that Allah has forgiven all his future sins?
It's a fair objection by non-Shias, one that made me think alot before I left Shi'ism. The issue is much more complicated for Shias. First of all, with no right and clear text they include 9 descendants of Al-Hussein (ra) in that verse (yet exclude the wives in whose houses this verse was revealed!!!), second of all, Shias do not just believe the Imams were pure before death, Shias believe the Imams are made from light (like Sufis believe), created before their own father Adam (!), having circulated the Throne of Allah and from their lights Allah created everything else. I can back up each of these kufri and alien statements from Shia books and their scholars speeches. As for why the Nabiyy (saws) makes istighfar then the answer is easy, our mother 'Aishah has narrated to us why (thanks to her we have this knowledge, after all in verse 34:33 Allah tells the wives to PREACH AND TEACH, no such verse about 12 Imams ANYWHERE in the Qur'an):
Aisha reported that when Prophet Muhammad (peace be upon him) occupied himself in prayer, he observed such a (long) qiyam prayer that his feet were swollen. Aisha said:
“Allah’s Messenger, you do this (in spite of the fact) that your earlier and later sins have been pardoned for you?” Thereupon, he said: “Aisha should I not prove myself to be a thanksgiving servant (of Allah)?” (Muslim)So it was a matter of adab with Allah, he did it out of shukr, how is that comparible to a man-made belief of the 'Isma/infallibility of 12 individuals who suddenly need the Prophet to pray for their purification yet they are supposed to be purified even before the creation of the universe?! Heck, the verse says CLEARLY in Arabic (and I am an Arabic speaker):
INNAMA YUREEDULLAH (إنما يريد الله ...) "verily Allah WISHES/INTENDS to ..." and not "Allah has already purified you but Allah wants to upgrade your purification" this is your own interpretation that clashes with the language of the Arabs, the basis of the Qur'an!
# Is/Was Nabi not included himself amongst his "Ahl al-Bayt" that Allah intend to purify?
He was, but the verse is obviously about wives and THEIR obligations not the Prophet (saws).
هذا وصل الله وسلم وبارك على سيدنا ومولانا محمد وعلى آله وصحبه وسلم