hey in what circumstance can you go to the airport and more importantly where in the airport to get your passport stamped if your on an ETA?I am not a lawyer but I will try to help you. I opened my own application (I got nothing returned back and already got my OWP so I am guessing I have filled it up semi-right).
Section A:
Applicant, Spouse - try putting in Martial Status of both of you - "Married-present" - in the guide they ask you if your wife and you were physically present at your wedding so the present would indicate that you were physically present at the ceremony (unless it was different).
Her mother and her father - their FULL names in English and in her native language, their place of birth, martial status and current address
Section B:
Not Applicable - meaning you and your wife don't have any children together or "separately" . I would also suggest filling up the table and all the rows with the word Not Applicable in this section. I have been told that leaving blank spaces might be taken as a mistake so I think it is better to fill that section up with Not Applicable - just to be safe.
Section C:
I think mentioning her brother is just fine, you don't need extra proof that he is your brother or that he got married. Fill the table with his name, their relationship - brother, date of birth, place of birth and his martial status I am guessing he is married.
Q2: From previous posts - I believe you have to wait again to get AOR but I think it might be faster - approx 4 weeks or so.
Q3: The IRCC wants you to maintain your visitor status BY YOURSELF so if she does not get the OWP on time (mine took less than 3 months to complete) she will have to apply for the visitor visa extend 30 days before her visa expires. I am not sure if she needs a visitor visa or she just simply gets a stamp in her passport at the airport but from my personal experience (Toronto, Ontario) as a person who needs only an eTA to enter Canada I could extend my stay for another 6 months by simply going to the airport and asking the officer for the extension (aka another stamp in my passport) which would extend my stay for another 6 months. If she does, simply apply for a visa extension (as a new online application) around 30 days before hers expires. I believe during the waiting time for the decision she gets an implied status till the decision on the new application is made. I would recommend looking that up.