a yahoo answer (ok, not the best source, probably close to the middling!) says the PErsian empire was 35- 70 million. even this concurs with the 70 million number.
Because Persia was the entire stretch of ancient civilisational lands from the indus right to Ionia, it had to have been more than 10 million.
Let's assume a 13 mill Greek added to 70 mill Persian, so the Greeks would have been about 13% of the Empire -- the rest of your statement about Rome seems accurate to my mind, especially the "industrial revolution" occuring a good 1800 years sooner
Not so sure about the no Messiah bit.
On the other hand, those analyses usually discount the cleverness of the Greeks in turning from wheat to olive trees. The Athenians weren't the only folks to figure out that olives, credit unions, and trained militia were great ideas!
Greece's quite successful colonial era began way before the creation of a single polity under Philip and Alexander's crowd.
Another "plus" is the cause of so much conflict between the Greeks and Persians ~ that was the emigration of vast numbers of Greeks into Western Anatolia! In the end the Persians could do nothing about that.
And what happens to Israel and The Messiah when Greece fails to spread its culture into the Middle East proper on the current time table? Well, that gives the Italians the "edge" over the Western Greek interests around the Mediterranean ~ (France/Gaul/Sicily) ~ thereby preventing the acretion of Iberia to the Carthaginian interests (and with that, the elimination of a component of the Messianic prophecies that call for The Messiah to tend first to the lost tribes ~ they'd simply not been there in Spain where He could sail to them. The whole place would be speaking Latin with no protective Greek colonies on the Mediterranean coast.
That'd necessitated a recalibration of the Messianic schedule.
Would this have given the Druids the edge? Maybe, but most likely disruption of Greek advances to the Western Mediterranean would have also stymied Gaelic speakers from getting to the Northwest coast of Iberia, and using that place as a springboard into Scota!
There may well have not arisen the Ireland we've all known to revere ~ instead, there'd be a more impoverished place with no cultural tradition beyond chasing cows and looking for all the world like Southern Chad!