You know, you really answered your own question. (The one you send me privately.)
-- The reviews are published by filling out a form which on submit pre-formats the results with HTML,CSS and Microdata format as needed and outputs the results to a file which is then brought into a HTML page using a PHP include statement when the relevant HTML page is served to the browser.
And therein lies your mistake.
Instead of outputting the reviews to a text file, they should be stored in a database.
And part of what would be stored, besides the preformatted HTML of the review, would be any fields needed to easily calculate the needed totals/values via a SQL query.