The Ash‘ari school and Maturidi schools have represented the ‘aqida or “tenets of belief” of the majority of Sunni Muslims for more than a thousand years; just as the Hanafi, Maliki, Shafi‘i, and Hanbali schools have represented the shari‘a or “Sacred Law” for the majority of Sunni Muslims for this period. Those against these two traditional schools of tenets of faith are people of bid‘a, defined in a fatwa or formal legal opinion by Imam Ibn Hajar Haytami as “whoever is upon other than the path of Ahl al-Sunna wa l-Jama‘a, Ahl al-Sunna wa l-Jama‘a meaning the followers of Sheikh Abul Hasan Ash‘ari and Abu Mansur Maturidi, the two Imams of Ahl al-Sunna” (Haytami, al-Fatawa al-hadithiyya, 280). In the past, such contraventions, aside from Mu‘tazilites, Shiites, and purely sectarian movements, were confined to a handful of mainly Hanbalis, whose bone of contention with the two traditional schools was that neither had anything to do with their literalist, anthropomorphic understanding of Allah Most High, which they promoted by all means at their disposal.
In answer to your question, the claims that Imam Abul Hasan Ash‘ari (d. 324/936) repudiated his own positions are not new, but have been circulated by these Hanbalis for a long time, a fact that compelled the hadith master (hafiz) Ibn ‘Asakir to carefully investigate this question, and thesanads (chains of narrators) for the attribution of these repudiations to Ash‘ari. The results of his research furnished probably the best intellectual biography of Ash‘ari ever done, a book that rebuts these claims thoroughly and uniquivocally, called Tabyin kadhib al-muftari fi ma nusiba ila al-Imam al-Ash‘ari [On showing the untruth of the liars, concerning what has been ascribed to Imam Ash‘ari], that proves that there are liars in all thesanads that impute this to Imam Ash‘ari. The book is in print, and whoever would like the details should read it.
Imam Ash‘ari’s al-Ibana ‘an usul al-diyana [The clarification of the bases of the religion] was not his last book, but rather among the first after he broke with Mu‘tazilism. Imam Kawthari states:
The Ibana was authored at the first of his return from Mu‘tazilite thought, and was by way of trying to induce [n: the Hanbali literalist] Barbahari (d. 328/940) to embrace the tenets of faith of Ahl al-Sunna. Whoever believes it to be the last of his books believes something that is patently false. Moreover, pen after pen of the anthropomorphists has had free disposal of the text—particularly after the strife (fitna) that took place in Baghdad [n: after A.H. 323, when Hanbalis (“the disciples of Barbahari”) gained the upper hand in Baghdad, Muslims of the Shafi‘i madhhab were beaten, and anthropomorphism became the faith (‘aqida) of the day (Ibn Athir:al-Kamal fi al-tarikh, 7.114)]—so that what is in the work that contradicts the explicit positions transmitted from Ash‘ari by his own disciples, and their disciples, cannot be relied upon (al-Sayf al-saqil, 108).
This is borne out by hadith master (hafiz) Dhahabi in his Siyar a‘lam al-nubala’ (15.90), as well as Ibn ‘Asakir’s Tabyin kadhib al-muftari. As for seeing dreams, dreams may warm the heart, but they are not a proof for either Islamic law or tenets of faith. In his introduction to Ibn ‘Asakir’s work, Kawthari notes that “the anthropomorphists are the ones who seem to need this [relating of dreams]: when unable to prove their point while awake, they go to sleep, to find the proofs they are looking for while asleep, to fill their books with them” (Tabyin kadhib al-muftari (21–22).
In relation to your questions in general, it is noteworthy that Saudi Arabia has printed and distributed worldwide thousands of copies of a Salafi book called Manhaj al-Asha‘ira fi al-‘aqida [The methodology of the Ash‘aris in tenets of faith] by one Safar Hawali, a professor at Umm al-Qura University in Mecca. It ascribes to the Ash‘ari school the misrepresentations typical of that part of the world, identifying the school with the positions of heretical sects like the Jahmiyya, the Qadriyya, Murjiites, and so on, and contains a number of the things you asked about the Ash‘aris, so I would guess this is the misinformation that your English Salafis are going upon. One can find the details in Hasan Saqqaf’s recent rebuttal of the work entitled Tahni’a al-sadiq al-mahbub, wa nayl al-surur al-matlub, bi maghazala Safar al-maghlub [The greeting of the beloved friend, and attainment of happiness sought, in affectionate discourse with Safar the defeated]. I have heard that Hawali has since moved on from his positions, though I do not know the details.
Saqqaf also talks in his work about the bogus Hanbali “repentances” of various Ash‘ari Imams such as Ash‘ari, Juwayni, and Ghazali, that don’t appear in their books but have rather reached us by sanads each containing an anti-Ash‘ari or two, as is also corroborated by Ibn Subki in hisTabaqat al-Shafi‘iyya al-kubra [The greater compendium of the successive generations of Shafi‘i scholars] under the biographical entries on each of these scholars.
From the wider perspective of Islamic law, these forgeries are rather meaningless, since a Muslim may not believe in the Islamic faith (‘aqida) of Ahl al-Sunna merely because his Imam has said it, but rather because he sincerely believes it is the truth. Scholars say that it is not legally valid to follow qualified scholarship (taqlid) in tenets of Islamic faith (as opposed to rulings of Islamic law) unless one has full conviction of these tenets of faith from one’s own heart—which is why they tell us that one’s faith (iman) by taqlid in such tenets is only legally valid on condition that if one’s Imam were to cease believing something of them, one would not. So the forgeries would seem to have little scholarly relevance, other than to show the lengths to which their perpetrators were willing to go.