Just FYI, for others who may be having the same problem, the only solution that works that I've found is the one mentioned in this thread:
http://https://www.mobileread.com/forums/showthread.php?t=100625
That is:
Thanks, I forgot to do that. So, in the end, I deleted the stylesheet, the page-template.pgxt, removed the reference in the opf file, and then converted in calibre with my css override. Annoying, not the cleanest file/workflow, but it worked.
Thanks to Slantybard.
If anyone could come up with something better and less "messy," please do tell us about it. Thanks.