I'll give you my opinion on a couple of your questions and leave the AJV specific questions for one of the boys!
#2) they can and sometimes they do offer a slot to the other company (this was my case) It is ok to express your preference during the interview but I would remain flexible, both are very good operations and I'm sure you will be happy on the AJX side as well if that would be the opportunity given to you (opportunity being the key word)
#4) No, their fee has nothing to do with your contract
#5) We had an F/O from AJX leave recently due to personal issues, something related to a family member illness for what I understand, It was so urgent in fact that he couldn't give the company the 90 days notice required and had to pay a large fine for what I understand, ouch!
We have a captain that left for another contract on the 777 that is coming back to AJX early next year