You should assume that getting upgraded at the gate will be next to impossible even though F is pretty open now. That is a popular time for elite travelers and I think they still serve some kind of snack during both your flight times in F.
Now if you can eventually earn AS Gold with your new job then I would say you would have a good chance at getting upgraded 72 hours out unless there are 10 Golds already on the list which could also be the case.
I am not sure I know what you mean when you say you will pay the difference to get an aisle seat. Did AS start a NWA system?