Timeline? (and other questions

We know that this is a 100 years after the Manga finale. But how long has Kurt Meyer been in power? My guess would be around 20 years, but I don't want to cause inconsistencies.

Secondly, is the 100 years there so that, chronologically, the canon characters have all died off (so no-one can mess around with being Roy Mustang's and Riza Hawkeye's child or something), and includes no major technological advancements?

Further, you'd think policies such as Kurt Meyer's would be too unpopular to arrange a coup on their own. Might there be another organization behind it, perhaps after another Philosopher's Stone?

Sorry, late reply.

About 20 years would be a good estimate.

Yes, that's the general idea behind the 100 years. We don't want it too far into the future (no humongous technological advances) but not too far in the past to be dealing with canon characters.

At the moment, there have been no revelations concerning his policies and such. For now, it is left entirely up to speculation for the resistance to decide why they dislike him/his policies. (More plot should come out eventually.)