A good fitting socket and impact will almost surely break those free. Honestly they don’t really look bad at all. Or a good fitting boxed end wrench and hammer on it. Though the position may be a problem. Penetrant will help I second the 50/50 trans fluid acetone or Kano Kroil stuff works far better than any other I’ve tried.

Distance from the refiner is not really of any importance to the station. The distance from the midstream where is blended and stored might but generally after it’s made it’s shipped via pipeline to a “blender” where it goes out buy truck to the station.

The sellers of fuels gas and diesel essentially buy the fuel from the market the either have the refiner or another midstream company mix or blend it with their additive package. The fuel that comes out of a refinery is basically the same “finished product”. The end user will have a contract with whatever company if they have additives they want then it will be blended before it hits the station. The real question you want to ask is what tier of fuel it is. Qt, BP, P66, Mobil gas stations all have the highest quality fuel. Circle K, ZX, and so on have a lower tier of gas. That said it all starts off the same way and the gas you get from any gas station was made at any refinery. If the station has a refining arm like Mobil, P66, Bp the fuel you get there likely didn’t all come from that companies refining they buy it on the market same as everyone else then blend and ship for sale. QT buys all of their fuel on the market and is blended the same way by all the refiners. One way or the other there is a very minor difference between top tier gas and bottom tier gas the you will not really see any Ill effect from possibly more carbon buildup on valves or something like that but it’s not really proven true and the engine in said car has more to do with that than the fuel. If you have a worry go to the name brand gas station.