Being situational aware will help in this case.
Yes. Though, to be fair, in certain situations it's intensely difficult to do that given the structure of the facility, the number of people/vehicles there at the moment. It's not always possible to see inbound lanes at all times, to any distance that would matter in a snatch-and-grab type attack that sought one's keys or control over the car.
I, too, do the same thing. The head-on-swivel approach works well for me, if resulting in nothing more than showing I'm aware and not going to be taken lightly.
If they demand the keys of me the keys come with a very high personal price..
That's what I attempt to do. Make it apparent that going that far is going to likely involve more than they're prepared to attempt.
One thing about Oregon is that they don't actually allow citizens to pump their own gas. So, basically, you sit in the car while the employee does the pumping. Changes the mix a bit, but it can still be rough when there are many others around.
Whatever else is true, SA helps. As does keeping control of your keys, wallet, entry into the car, etc.