So, I was able to CAREFULLY rework the code, fixing what I thought might be the problem. Zipped all the corrected files to him after testing in several browsers and my phone and iPad, that it did, indeed, work as intended.
He re-installed everything, but once again, the HTML file converted to a PHP file, and he saw the same junk code on his page.
After *deleting* all the files on his site, and reinstalling the new files, his site worked as designed.
2/3