I understand that you are facing the problem of low GPU load and low FPS after some time in the game. This can be a frustrating problem, but there are several ways to solve it. I had the same problem when playing pokieslab.com . I am just a fan of the pokie machine and didn't know that my video card needed the right drivers. My advice from experience is to make sure your video card drivers are up to date. Outdated drivers can cause performance problems, so keeping them up to date is important.
Another thing you can try is to monitor the temperature of your GPU. If your GPU overheats, it can reduce performance to prevent damage. You can use programs like MSI Afterburner or HWMonitor to monitor the temperature and adjust the fan speed accordingly.

Rather than testing 1080p performance -- which you never use for any other reason -- and rather than testing what happens if you unplug your monitor in the middle of a 3dmark benchmark run, why don't you just happily play the game which works perfectly fine normally?
Why were you banned on other forums? Was it because your hardware hypochondria was interpreted to be a desire to waste of people's time?
You should pursue a career in bug testing. It seems that is your passion.

Also when i go to 1440P this issue not happens. On 1440P i have most of the time 100% usage and stable fps. So i think i will stick on 1440P.

Ok thx