I would probably argue that many historians used to take a top-down approach to discussing life under the Regime. Different interpretive choices have also coexisted and continue to do so. I would not regard De Felice and Santarelli – to cite two, quite opposite, examples of Italian historiography of Italian Fascism – as falling within the same interpretive model, even if they both rely heavily on what can be described as “top-down” inference process. Traditional historiography – at times improperly, referred to as “neo-Rankean” - and firm Marxist “structuralism” - both have a tendency to regard certain sources as spurious, or anecdotal, and therefore less valuable in outlining a general picture.

Leaving aside the – quite dated – controversy over the issue of “consensus/consent”, and looking at the various historiographical schools and currents from a considerable distance, I do not believe there is a definitive answer as to what way works best in providing a proper understanding of “Fascism”. The economical sphere, the organization of the production process, demographics; political parties and currents of the public opinion; diplomacy and military matters; all represent portions of a picture which begins to make sense in its relation to the lives of the people who inhabited it. But one probably needs all those things together. As I was writing the other day, I do believe that any interpretive choice needs to be evaluated in its relations to the concrete historical process under examination, and especially in so far as what relations it's able to illuminate and, in some way, to create. As the “historical process” is ultimately composed by people in their individual and collective relations to “time”, there certainly is a need for “everyday life”.

This is not really absent in traditional historiography either. There's a footnote in Vivarelli's Storia delle origini del fascismo (vol. 2 I think) which has always stuck with me; because it's inclusion – from a “traditional” perspective – would feel almost gratuitous. It's a brief excerpt from the funerary speech for a young women who had died of a work related illness, delivered by one coworker – a friend – of hers. It speaks of “socialism” and hope, but gives the reader nothing to reinforce Vivarelli's general argument; but, even in a book that had to contend with the publisher for the excessive footnoting (Italian publishing didn't work the same as British and American), I can see why he didn't cut that one.

More recently, a historian who certainly doesn't belong to the “new wave” of Fascist studies, such as R. Bosworth, has authored a text on Mussolini's Italy which explicitly promises to tell us something of life under the fascist dictatorship (2014). While his choice is (partly) driven by his polemical (albeit not entirely unwarranted) take on the current state of historiography on Italian Fascism, his intent appears more or less to provide an attempt to recreate those connections between individual experiences and “the bigger picture” that I was discussing before.

To address the second part of your question, I feel that you are (at least in part) missing the point. The access to sources is indeed an issue, as Kate Ferris correctly points our in the introduction of Everyday Life in Fascist Venice (2012), as well as a recurrent criticism leveled against every “other” historiographical approach.

Sources are what they are (incidentally, there are far, far more letters and diaries from one-hundred years ago than a thousand historians can read in a lifetime). The historiographical issue is how to interpret them.

To go with your example – De Felice's work on police reports in order to gauge the state of public opinion under the Regime – much maligned as it is, his work, I believe, supports his fundamental conclusion: that the Regime found no particular reasons of concern with the state of the public opinion. Given De Felice's perspective and interpretive choice, it says almost nothing else, and it's a fairly important matter, as there were moments when this concern certainly existed and motivated different actions and reactions.

This limitation, though, is not inherent to the source. The source could tell us more. Marxist historians during the 1970s and 1980s have examined court records and court-martial records to find evidence of the antagonistic relations between the masses and the authority. If De Felice used police reports “as they were intended”, historians like Giorgio Rochat used them not only to challenge, but to subvert the intended meaning. Possibly opening the way to a better understanding of how the text represented a negotiated space of dialogue.

The text alone – writes Ferris – cannot signify cultural praxis; it is only when we take into account the way in which readers ‘used’ the texts they read (or images they saw, or rituals they observed and participated in) that the relationship between the cultural forms represented in the text and subjective lived experience is brought to light. […]

Police reports may be profoundly revealing of the author's worldview, more so because they are so deeply limited in what they can discuss. They need to convey information, and meaningful information, information that is deemed meaningful by both the sender and the receiver and, possibly, understood by both ends to mean the same thing.

You are unlikely to find a diary by former prefect of Ferrara S.P. describing how he felt about the actions of the fascist squads within the province. You may speculate on it based on his subsequent career, or rely on opposition sources which accused him of complicity (but this happened all the time). But you can read his telegrams to the Interior, and they tell you very clearly that the author believed the fascists were right - over the top, perhaps – but fundamentally and morally aligned with the duties of his administration.

Gasti's report on Mussolini is well known. But it's not merely a source of information on Mussolini: it tells us by what means the author understood a personality of interest. Things like: does this report draw any connection between an individual's criminal behavior and their race, or gender, or religion? Once we begin asking ourselves such questions – which is very basic stuff if I can do it – then we are no longer stuck in an inevitable “top-down” approach regardless of what sources we have available.

What is crucial – continues Ferris, citing Ginzburg's famous The cheese and the worms – is that although, like all historical subjects, Menocchio and his particular worldview were unique to him, his uniqueness, like that of all historical subjects, operated within determined limits. He operated within the limits of what it was possible to know and do in the time, place and milieu in which he lived: he is analysed as the ‘exceptional typical’ of his environment. Thus, from his individual story it is possible to deduce wider observations about the culture of his society, based on the parameters of thought and modes of behaviour possible. The same is true for our context of fascist dictatorship. […]

As noted above, I am not particularly proficient in this kind of history. I would suggest you check out Ferris' introduction and recommended readings for a more in-depth approach to methodology. But I hope this brief answer may be helpful to you. And feel free to ask for clarification if I left anything out.