I believe you're close to correct. According to a paper in 2013 by Graham Coop (an evolutionary biologist from UC Davis) every living person of European descent, if you trace their family trees back 1000 years, likely shares the same list of ancestors. And that list of ancestors is more or less all the people alive in Europe at the time who had descendants surviving to the present -- about 80% of the people alive at the time. Joseph Chang, a statistician from Yale, has also written a great deal on the subject.
A direct paternal-line descendent of Dante, which Sperello Alighieri might very well be, would essentially share a copy of Dante's Y-DNA, which is about 2% of the human genome. This is comparable to something between 2nd cousin (3.13%) and 3rd cousin (1.5%).
I was in a book club dedicated to reading Finnegans Wake, all 626 pages. We met every two weeks over dinner and would discuss a page or two, or sometimes just a paragraph if things were especially puzzling. It took us eight years to complete.
I agree with Wells about the frustrations with the endless riddles and the incessantly opaque style.
However an unexpected pleasure was how much fun it was to read in a group. For example, a set of allusions sprinkled on the page might catch the eye of someone for whom the subject was a pet interest or hobby, otherwise we all would have missed it. I learned a lot about world history, art, philosophy, etc., and I almost always ended the evening astounded at the oddest bits of information my friends had tucked away in their heads.
Finnegans Wake works really well as a scaffold for learning and conversation; as a story, I'm not so sure, but I think it is a remarkable literary experiment. There are also several truly beautiful passages hidden away in the book, which hit you by complete surprise when you stumble on them.
Gambit Scheme is also a pun on Marc Feeley's surname in Irish -- O Fithcheallaigh -- which means 'chess player'. The name is derived from the ancient Irish board game fidchell, rules unknown, but taken to be akin to chess.
Not the most detailed link, but illustrative:
https://www.ucdavis.edu/news/one-big-european-family-video/