The cpu usage is a result of your low gpu usage.
Thats why we need to get the game to utilize your gpu more.
You want your gpu to run at near 100%. thats when you get the most out of your gpu.
It's really odd that nothing works for you.
Do you happen to own any other EA games made on the frostbite engine?
Previous battlefield titles, anthem, battlefront? Or can you download a demo of one of them.
I think all of them have 10 day free trial. Preferable battlefield 1 and anthem.
I just want you to check what happens with those games regarding your gpu usage.
And one more thing. Does this happen both in multiplayer and single player?
And please try to disable HPET.
Also can you confirm that your cpu is actually running at max clock speed and using all threads?