I think you're exaggerating the difficulty. We have more than sufficient documentation of many facts to make definitive statements about them, and where we are not sure abou ttheir provenance we can qualify our statements as being limited to a sinlge source or being controversial. We could, for example, dispute the historical causes of the Battle of Waterloo all day, but there's widespread agreement that it took place 200 years ago next Thursday, who the principles were, how it proceeded, and what the outcome was. Of course there are numerous details about the event that event that remain the subject of historical inquiry; did Wellington meet Blucher at 9pm or 10pm, and where on the battlefield did this meeting take place?
It's certainly true that any historical incident comes with a mass of unanswered questions, sometimes of great import - witness the ongoing controversies over the assassination of Kennedy or the authorship of the September 11 2001 attacks in modern times. But there is little dispute that that assassination and those attacks took place on those dates, what the basic nature of those events were and what major changes ensued in the aftermath. Although we face significant epistemological limitations in studying history, you seem to be arguing an almost solipsistic position, as if the impossibility of knowing everything invalidated the notion of knowing anything.
Matters of fact (even if wrong) can be linked together into a web of evidence and assumptions and would serve at least to illustrate what we know and don't know.
It's certainly true that any historical incident comes with a mass of unanswered questions, sometimes of great import - witness the ongoing controversies over the assassination of Kennedy or the authorship of the September 11 2001 attacks in modern times. But there is little dispute that that assassination and those attacks took place on those dates, what the basic nature of those events were and what major changes ensued in the aftermath. Although we face significant epistemological limitations in studying history, you seem to be arguing an almost solipsistic position, as if the impossibility of knowing everything invalidated the notion of knowing anything.