I followed your instructions.
It didn't work BUT, there is a conflict with FF and Outlook.com (both parties aware) and in order to tolerate using OL, I switched to the beta version. At this point, it no longer has OWA in the search bar.
It is now just this: https://outlook.live.com/mail/
When I switch back to the non-beta version
, it works fine (so far).
It works fine still in the original outlook page (w/owa), but if you have a solution for the beta version, I would appreciate it.
Mozilla said there won't be a quick fix -as evidenced by today's update.