My only nit is with the following as the rest of your post is a well measured, thoughtful analysis.
My primary concern was that this thread is over-emphasizing the relative risk of being caught in a terror event.
If you take the whole of the USA and jumble in the 10s of thousands killed or injured during 9/11, this is indeed true.
If you take merely the number of people in Manhatten at the time, or folks like myself who watched it from across the Hudson, your percentage goes up significantly. If you were in WTC 1 or 2, your risk was 100%.
My mother and father live in small towns in Ohio. I work in southern Bergen county NJ, I travel into Manhatten on occasion. Who's risk is higher?
My point is that one needs to factor in proximity to high value targets to identify risk as best as possible. Calculating risk by using the population of the country or the world as a benchmark is disengenuous.