Quick update: I’ve installed Weaver Xtreme Plus 7.0.3 on my sandbox site and removed the temporary CSS workaround I had added for the top post info line/calendar icon issue.
So far, 7.0.3 appears to have fixed the problem. The Custom Post Info Lines section is visible again, and entering the following in both Top Post Info Line and Top Post Info Line (Single) restored the display correctly:
Posted on %month% %day%, %year%
One interesting thing: on the IMC-Lewes sandbox site, those fields were blank, so I had to re-enter the custom line manually. I’ve also tested Hattie’s Garden and updated the production side there, and that looks fine as well. For now, I’m leaving the IMC-Lewes production site alone since that one involves a little more surgery, but 7.0.3 does seem to have resolved the issue.