Oh my, that explains a lot! These settings are significantly higher than they should be for your computer's spec. Some settings to change:
Texture Quality. Try lowering down a notch or two (or three). Right now X-Plane is trying to load around 10 GB of textures into VRAM (much beyond what your graphics card has) so lots of texturing paging would be going on, slowing everything down significantly.
World objects at high: If your CPU is a bottle neck, lowering this a notch should improve things
Visual effects. If the GPU is still the bottle neck, lowering this a notch would help