I have been trying to track down a future history which was published on the Internet around 20 years ago. Would be classed as "space operatic" now, but a story of the human race, rather than stories of protagonists. It was broken into large sections covering a good 10-20,000 years in some detail, and well beyond that in less detail. Near space adventures, solar system colonisation and conflict. First contacts, FTL drives, inter-species wars.... Anyone recall this? I have searched on the net an can find no references.
Olaf Stapledon's Last and First Men sort of fits the description although some aspects you list are not present. Maybe a book someone interested in what you are looking for also would like.
"No book before or since has ever had such an impact upon my imagination," declared Arthur C. Clarke of Last and First Men. This masterpiece of science fiction by British philosopher and writer Olaf Stapledon (1886–1950) is an imaginative, ambitious history of humanity's future that spans billions of years. Together with its follow-up, Star Maker, it is regarded as the standard by which all earlier and later future histories are measured.
The protagonist of this compelling novel is humanity itself, stripped down to sheer intelligence. It evolves through the ages: rising to pinnacles of civilization, teetering on the brink of extinction, surviving onslaughts from other planets and a decline in solar energy, and constantly developing new forms, new senses, and new intellectual abilities. From the present to five billion years into the future, this romance of humanity abounds in profound and imaginative thought.
Could be Asimov's Foundation series? Very operatic in tone, right on with the timespan and differing levels of detail per "episode" along with differing scope re:near space/solar system colonization/contact rules/jump drives/I even think there was some interspecies conflict at some point.
Additionally, a lot of this work was posted on the internet in the 90s, but it's hard to find anything of his just free-floating on the internet in full other than stand-alone stories now.
Could it be Mike Resnick's Birthright: The Book of Man? It's the future history of mankind conquering the galaxy, losing control, and eventually dying out. It was published in 1982.
Birthright spans a timeline of nearly 17 millennia, beginning at a very early stage of expansion from Earth and ending with the death of the last humans. In between, it chronicles a slow but (despite some set-backs) steady conquest of the entire galaxy - inhabited by thousands of sentient alien races, which are overpowered and oppressed using whatever tool it takes: economic pressure, diplomatic finesse, or simple military power.
Not all chapters deal with humanity's treatment of aliens; some also cover the "internal" politics that result in a development of the growing human empire from a democracy to a monarchy. But the biggest theme is undeniably the search for the elusive quality that allows humanity to overcome all opposition and manage the unique feat of conquering the entire galaxy. It is never clearly defined but manifests perhaps most succinctly when it also results in the failure of an attempt to cross the void between galaxies.