Thank you for being forthright. The article itself is constantly changing the yardstick of measures, from the top 1%, top 10% and top 20% across the various text and charts and the chart you reference adds up to 100%. This article I found from 2016 indicates that:
"Foreigners currently own about 25% of outstanding corporate bonds, 15% of American stocks and 12% of agency securities (a category that includes mortgage-backed debt)."
https://www.marketwatch.com/story/how-much-of-america-do-foreigners-really-own-2016-09-27
As for your last statement, "won't be long before the top 50% own as much total wealth as the bottom 99% all put together", These percentages overlap so significantly, that the statement becomes meaningless.
Rather than have a long boring discussion about this problem you have with wealth distribution, how about you just present your final vision of wealth distribution. What is the maximum wealth gap between the poorest person in the US and the richest person in the US and how you intend to get us there. Fair enough?