I do not have duplicate scenery at the moment.
It's in THAT screenshot, which was one you explicitly said you should have a look at.
my screenshot of your post above, surely indicates your scenery is putting too much stress on DX9
That screenshot of yours only indicates you have a duplicate scenery. And it's exactly the opposite, THAT one probably put too much stress on your system, causing low fps. And, as I've said already, MY 51.2 fps WERE OBTAINED IN DX9.
I took this 10mins ago
It's possible the duplicate scenery is not showing now, and this MIGHT still be due to the fact your system IS under stress and can't even display it, but that doesn't mean is now slowing down anyway.
And, It's now 7th time in a row that you managed again to dodge my question:
A default airplane, in 2D panel view, without the 2D panel, and with the fps set to Unlimited. Try to set the plane in a position similar to my first screen that showed 51.2 fps, and give me the number, please.