Penguin, . . .
In a way, I have a hard time getting in your shoes, but I'll try.
First off, if my wife and I are together, . . . 95% of the time, I am the driver, . . . and I am the one that gets the gas. I do it by lightly surveying the station before I get out, . . . and by making sure the station is not in a "bad" area. She stays inside, . . . generally belted in, ready to leave.
I always put the nozzle in and lock it back, . . . then I just keep observant. If you were near me, . . . you would probably think "girl watcher" or something like that maybe, . . . I try seriously to keep it low key, . . . but I know who is in front of me, behind me, and on both sides.
Paranoid? No. Observant? Definitely. Armed? Most of the time.
The other thing you can do, is improve your image. Ditch the geeky clothes, and grab something a bit macho. You are very much 100% correct that it is easy to spot an individual who appears to be an easy mark. You may still be one, . . . but you don't have to advertise.
May God bless,
If you can breathe, . . . thank God!
If you can read, . . . thank a teacher!
If you are reading this in English, . . . thank a Veteran!