It seems a driver update fixed it for me. Edit: not true, the black reflection bug seems only in some track variants. But horizon was still too high.
I had this issue when using Nvidia Surround with corrected bezels and using the resulting custom resolution in-game. (Like you I also set the triple monitor launch string bezel value to 0 because I expected bezel correction to be properly catered for in-game) I resolved it by adding a bezel value within the launch options and also switching back to the original native resolution, (7560 x 1440), rather than using the custom one. Everything seemed to line up slightly better as well in terms of cockpit FOV, with any adjustments easier to make. It's as though Surround bezel correction and the custom resolution generated isn't properly recognised / implemented so you still need to make the adjustments in the launch options and video settings. Might just be me though!
I tried the same but nothing changed. With bezel width 1 and 5760x1080 or bezel corrected 5900x1080 the result was the same. So i went back to 5900x1080 and bezel width 0.
Changing all values while in game would make it a lot easier. But that option was going to be added in a later stadium iirc ?
I have just watched a "Goodbye-Ruf-Video" on Youtube and noticed that the same issue appears in VR (@4:27)