I'm not sure about your departure questions, but I think when you exit the baggage and customs hall in F, you can just take a left instead of a right. That's how you go for connecting flights but I cannot remember if you have to show a boarding pass or anything. I don't think so but I'm always so out of it after long flights. So instead of taking the right and walking out into the terminal, just go left as if you were connecting and then hop on the train. It's all the same passport control, the decision to connect or leave is the last step.