Honestly, you're probably out of luck then. Without fail, ZUN sells every copy of whatever game he puts out at Comiket/Reitaisai within hours, but I imagine that how much he actually prints of a game each time is not exactly... documented (could be wrong here, but idk where to look for sources). This is completely discounting the fact that you will find physical copies in just about any doujin shop, and even more general stores at this point as well (here's a tweet of Touhou games and merch being sold at Narita airport lol:
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This is further discounting the fact that digital sales exist now
aaaaand finally I'm certain that given the hilarious ease of acquiring Touhou less than legally, a lot of people have probably just... pirated it (especially in the west. Getting
any official Touhou game pre-mid 2010s in the west was difficult for a number of reasons.)
I'm not going to provide a link (because rules), but a Western Touhou centered forum where you can easily download all the games has EOSD sitting at just over 100,000 downloads. Keep in mind that the file was uploaded to that website in early 2018, so that's literally over a decade of piracy unaccounted for, from... wherever Touhou was illegally downloaded in the west before then. Also discounts all the other games too.
tl;dr
finding out how many people actually played/pirated/bought the games is futile