To close/update this thread-
My solution was not a fix per-se, but rather a workaround:
When reinstalling Office 2011, I went the Custom Install route, thus forgoing Messenger, Remote Desktop, Visual Basic, Proofing Tools (except English), MS Document Connection, and Office Fonts.
So far, no keyboard issues and no alerts in Font Book. I remain hopeful that the remaining 231 fonts will suffice. If not, I can custom install
the MSO 2011 fonts later.
FWIW, I have never specifically added fonts, e.g., all are a result from OS & app installs.
For now, all is peace and light in Pendragonland.
27" i7 iMac (10.13.6), iPhone Xs Max (12.1)
Those who can make you believe absurdities can make you commit atrocities. ~Voltaire