No:
-Tools -> New Config -> Retain current configuration: All -> Apply
-Check all assignments and assign any missing disk(s) if needed.
-Start array to begin parity sync (alternatively you could select "parity is already valid" before starting the array, since it mostly is, then run a correcting parity check)
That won't accomplish much, best to replace or swap the cables with another disk to rule them out.
I suppose you mean unassign and re-assign the disk here, if yes that's correct
SMART test passed so disk fine, at least for now, and those pending sectors are "false positives", replace/swap both cables to rule them out and rebuild on top.
Not seeing any USB device being connected, but since the log is kind of long, reboot, start the array, wait a minute and then plugin the USB device and post new diags.