Silvia, there are discussions elsewhere on AFF re claiming compensation (not just 5000 points) for Qantas Frequent Flyer (or other airline FF) points 'lost' due to occasions like this. Be assertive, document every call and email/letter and keep at 'em.
Asking at check in tomorrow for J seats wouldn't go astray. These however are properly matters for chat in other sections of this blog.
Will the airline give you an hotel, transfers and meals tomorrow due to the 17 hours between flights? Again, no harm in asking.