I didn't read it all, Paula, because I have trouble reading thru beable-beable.
IMO, the Heritage paper analyzes an extreme position that nobody is taking, then tears it apart while hoping the careless reader will mistake the extreme position for its opponents's position.
It's called a strawman argument, and it's the kind of intellectual dishonesty I have come to expect from the Right. The math may be entirely correct for all I know. It's just irrelevant.
The argument on the table is to raise the cap enough to restore the wages covered by Social Security taxes to the 90% level. This is Robert Ball's proposal. With the shift of wages to the highest quintile, and the loss of real wages for the majority of workers over the last 20 years, FICA now covers only about 85% of wages. Before this shift, FICA covered 90% of wages.
There are good (IMO) political reasons not to lift the cap entirely.
-- Homines id quod volunt credunt.