I think I found an answer to one of my questions:
"...the plain meaning of s. 4(3) of the Immigration Regulations is clearly centered on the intention of a spouse at the time of the marriage, a situation that cannot be affected by a subsequent change of intentions on her part. Therefore, the applicant's spouse was properly adjudged not to be a member of the family class..."
from here reports.fja.gc.ca/eng/2000/2000fc26227.html
So, as I understand it, that if the reason for refusal of spouse sponsorship is that VO does not believe that the realationship is genuine, then the only option left is an appeal.
Please correct me if I'm wrong.