As far as I know:
If you do not receive an invitation for the ceremony within three weeks , then you should go and ask the immigration office in your area. They will tell you if you fail or not or have a hearing with a judge.This based on my experience.
If two people (wife and husband) applied together and one of them passed and the other failed they can easily separate their files and the one who passed the exam will receive a letter for his/her ceremony within a month of the date he/she applies for file separation. This based on my experience.
My spouse is confident she has failed the test. As per your experience separating the files is easy. I called cic and the agent stated that separation of files is not a routine and will usually not be processed.
English language is not a big problem , once you know the basic that is it.
If you pass the exam the judge will not ask you questions about knowledge of Canada this based on my spouse experience.