Well … Your system is a lot better than I had hoped so I’m pleased for you there 
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The only really obvious weakness that stands out to me may be your PSU but if that was the problem I would have expected your PC to be crashing to desktop or just periodically resetting itself and from what you say this is not happening.
So, there is something else going on somewhere which, at least to me, is not obvious.
Just out of interest what aircraft are you siming in? I fly in relatively light GA aircraft and my FPS would be quite a lot less if for example I simed in the Fenix A320.
Also, I have disabled photogrammetry (not a massive fan anyway so no loss to me), I don’t use live weather, and airport traffic is at 10% (using aerosoft simple traffic).
Other than this I’m beginning to struggle a bit
Edit: I just noticed you have the Fenix which some people think is heavy on fps. Is your bad fps also with other aircraft?
Edit 2: you state that your ram is 3200. Is it actually running at this speed. In my system, years ago, I had to go into BIOS and use an XMP option to increase my speed to 3000 which is the maximum recommended speed for my ram. A slow ram speed could have quite a negative effect on your PC performance.