I live in the Amish community referenced in this article and I have never seen nor heard of any corporal punishment nor child abuse. Indeed, I have never heard any Amish person even yell, scold or argue with anyone. Because of that, I am pretty sure such issues are rare in this area.
"People like to think that Amish teenagers have a choice about leaving the community, but what choice do they have when their prospects in modern life are so limited by their lack of education?"
Most Americans, Amish or not, do not become software developers, bankers, accountants, etc. Lots of Amish leave. For example, two doors down from my house there is an elderly Amish couple. All of their children are non-Amish but still support, visit, help, interact with their parents. Not surprisingly, most ex-Amish do not pursue fields requiring advanced education but tend to do very well in more blue core businesses where their work ethic, integrity and significant youth experience working at home can be turned into a solid career.