1. Be sure to
restart your iMac
before doing anything, and to run your commands without ever launching Safari.
2. ganbustein isn't clear about whether
defaults export domain_name someSaveFile.plist
and
defaults import domain_name someSaveFile.plist
supersede the commands you've posted or are alternatives, so if the ones don't work, try the others.
3. You've got to enter complete paths to the files with which you're dealing, NOT just their file names. (You can do it by dragging the files into your Terminal window at the appropriate points,
being careful to type in preceding and following spaces.)
4. I suggest that you run your command sets one at a time, beginning with TopSites.plist, because if you run them together, you won't know which plist is your culprit (if, in fact, one of them is).
