No need to run the game in administrator mode, this won't give it more resources. Not sure why this keeps coming up. More permissions is not equal to more resources.

But that's just an aside. So you say, your FPS drops to like 9 FPS, but you didn't specify how long it will stay there.

The game is not that optimized and FPS will tank sometimes for a very short moment. The FPS will tank very hard, whenever the game is performing a world save, but you can see this is happening because the game is telling you in the upper left corner.

Can you please verify if it is indeed the world save or just the usual micro stutters?