Will copy/pasting the known good data directory to the corrupted one solve the corruption problem? Is it as simple as re-booting and starting fresh with the one exception that the new program will have to re-build to the current height?
Yes. That's how any backup works. It's probably best to shut down Bitcoin Core before you start making your backup, you shouldn't copy it while it's being written to.
In spite of having a UPS and an AC/DC inverter for the house, I am now on IBD #3
How did that happen? For what it's worth: I prefer a laptop over the hassle of getting a UPS.
a. Copy/paste or delete old and replace new?
When restoring a backup, I wouldn't want to keep incomplete newer block files while restoring older files. If you have enough disk space, you can rename the damaged directory before restoring your backup. If you need it again, at least you still have it.
b. Ditto EXCEPT do this only with the blocks subfolder?
If your wallet isn't corrupted, you shouldn't replace it. Your backup won't have the latest transaction Labels.
the data increasing roughly every ten minutes, you would need to do a backup frequently
If you're a month behind, you'll only need to sync a few GB. If that's acceptable, you don't need very frequent backups.
I’m most interested in finding out if a complete backup and restore is possible.
I only backup data I can't reproduce. That's my wallet.dat. Any other data I'll just download again if I have to.