Clark has evidence from lots of countries, and I'm still surprised just how uniform the numbers are. Even in places where private property was all-but-outlawed for 2-3 generations in the middle.
As for the second, the rich have the resources to dodge or mitigate that kind of state action in all but the swiftest and most brutal of cases.
Re family status surviving Maoism or whatever: If you posit that there is something besides actual assets which is helps "dodge or mitigate", then I ask why this same something isn't in play in normal times. If it alone can explain the persistence, that weakens the case for assets mattering so much.
The other line of evidence is things like the Georgian land lottery, which elevated some people to quite significant wealth. Their kids lived well. But it's been, I forget, 150 years or something, and their decedents are no longer unusual at all.
The last. The article wants to make it sound like this is inherited wealth (alla Picketty) but this isn't really supported. For example, you find much the same pattern even across say the cultural revolution, which I hear was rather rough on inherited nest eggs. The rec. book on this (as in one of the old comment threads below) is Clark, "The Son Also Rises" ( http://amzn.to/2jFnUmZ ).