From a historian's standpoint, it seems like you're asking not about the Quran in particular but more about how historians read and assess texts in general. In Western Europe in the 1800s, as the academic discipline of history gradually emerged from antiquarianism and similar un-institutionalized approaches to studying the past, historians sought to present objective, verifiable narratives about the past. As the German historian Leopold von Ranke (1795-1886) famously introduced one of his works:

History has been assigned the office of judging the past and instructing the present for the benefit of future years. To such high offices the present work does not presume: it seeks only to show what actually happened.

Man hat der Historie das Amt, die Vergangenheit zu richten, die Mitwelt zum Nutzen zukünftiger Jahre zu belehren, beigemessen. So hoher Ämter unterwindet sich gegenwärtiger Versuch nicht; er will bloß zeigen, wie es eigentlich gewesen. (1824)

Historians since Ranke—and thus many people who have met historians trained in the traditions of Western academia—have tended to value historical works only insofar as they represent "what actually happened." For example, the great medievalist Hoppolyte Delehaye (1859-1941) went about trying to discriminate which biographies of saints presented facts and which ones were fictionalized. In his own words:

Of the two general types of texts we have encountered over the course of our researches, some of them, governed by events, have been described as historical, while others, coming from special inspiration, are classified among literary works. This division arises from the paradigm that opposes history to literature, the first of which is deemed to report facts that have occurred in their actual order, and the second of which reflects only ideas, in forms created by the imagination or by convention.

Des deux grandes séries de textes rencontrés au cours de nos recherches, les uns, dictés par les événements, ont été qualifiés d'historiques, les autres, issus d'une inspiration spéciale, se classent parmi les œuvres littéraires. Cette division répond à la conception qui oppose l'histoire à la littérature, l'une étant censée rapporter les faits qui se sont passés dans l'ordre réel, l'autre ne reflétant que les idées, sous des formes créées par l'imagination ou la convention. (1921)

This is, of course, not the only way to read texts. For example, people in medieval Western Europe—the very people who wrote and first read the texts that Delehaye was studying—would not have understood this division of history vs. literature. Instead, they tried to read texts—and especially the Scriptures—on multiple levels at once. There's typically four categories, but they can appear with different names. One common set is literal, moral, allegorical, and anagogical.

All that goes to say, the medieval authors of saints' biographies would likely have thought they were writing works that were both history and literature, particularly if they were including Scriptural references or quotations (which almost all of them do). The great literary critic Umberto Eco (1932-2016) noted that this approach to texts spans at least from St Paul to Dante. To take just one example from the great English theologian Bede (672-735):

In this way the Psalm might rightly be interpreted—"Praise the Lord, O Jerusalem; praise your God, O Sion. Because he has strengthened the bolts of your gates, he has blessed your children within you."—historically, regarding the citizens of earthly Jerusalem; allegorically, regarding the Church of Christ; tropologically, regarding the souls of all the elect; and anagogically, regarding the celestial homeland.

Simul modo quod dicitur: "Lauda, Hierusalem, Dominum; lauda Deum tuum, Sion. Quoniam confortavit seras portarum tuarum, benedixit folios tuos in te." De civibus terrene Hierusalem, de ecclesia Cristi, de anima quaque electa, de patria celesti, iuxta hystoriam, iuxta allegoriam, iuxta tropologiam, iuxta anagogen recte potest accipi. (De Schematibus et Tropis, as cited here)

Where does this leave historians today? Well, regarding medieval texts, we no longer attempt to divide them into texts that are historically 'accurate' by modern standards vs. texts that are second-rate pre-modern 'literature'. Doing so would indicate a profound understanding about what these texts were about and what they were meant to do. Instead, we try to appreciate and evaluate texts in terms of what their authors were trying to accomplish and communicate. And we closely examine how early audiences received these text, how they circulated, and how they impacted their cultural milieux.

As a result, we're moving away from many of the grand narratives constructed by earlier historians who sought to illuminate a shadowy past reflected through the sources. Instead, we're gaining a greater appreciation for the things our sources were written to do, and we're beginning to use these insights as a basis for writing new narratives about the past. (In my own field, Walter Goffart's Narrators of Barbarian History (1988) marked a general turn toward this approach.)

But what about the Quran? Well, it doesn't seem like I'm ethically in a position to help you pass judgment one way or another. But if you adopt tools of historical analysis such as those in use among medieval scholars—who have long wrestled with similar problems—you can set aside concerns of defining or defending literal truths for a more varied (and I hope fruitful) set of questions: Why did the author of the Quran (God? Gabriel? The Prophet or his transcribers?) first speak or write down these words? To whom were they addressed? What were they supposed to do? How were they received? What concerns did they raise? How were they resolved?

A lot of these questions can be explored through a close read of the Quran itself. Ibn Ishaq provides us a very early scholarly opinion (Biblical scholars should be jealous) about how the Quran developed, what concerns it initially raised, and how these concerns were resolved. And early jurists and scholars of hadith provide their own rich sources of information. Western-based academics are only starting to catch up to these authors of Classical Islam, but there's a few easy-to-access resources out there.

In general, I'd point to MAS Abdel Haleem's introduction to the Oxford World's Classics translation of the Quran (2008). Particularly for anyone who doesn't speak Arabic, I can't recommend Michael Sells's Approaching the Qur'án (2nd edn. 2007) highly enough. And to get a sense of how historians talk about the Quran in professional settings, it might be worth skimming through The Qur'an in Its Historical Context (2007).

TLDR Historians tend not to examine the accuracy or non-accuracy of pre-modern texts, since few if any of these texts were written with modern standards of accuracy in mind. Instead, we look at what texts were written for and how they were received. Ultimately, this has proven to be a much more fruitful approach for our own field, and hopefully, it may be a fruitful approach for your personal endeavors.