If others with identical systems run at higher fps it must be your settings?!
I suggest to agree on one mission (like SU-25T free flight) flown to compare fps and it is surprising that nobody using Nvidia cards ever mentioned the pre-defined profile that is coming with their drivers. It is named "Digital Combat Simulator: Black Shark", but the executable is "dcs.exe", so i guess that profile is active?!
Is "GeForce Experience" installed? I never installed it, because i distrust "automatically optimised pc settings for games". I use Nvidia Profile Inspector, delete pre-defined profiles and start from there.
CPU (4770) usage 40% - yes, but that is leveled over 4 cores, one core 70 one 40 and the other about 25.
GPU (980ti) usage 40-70%, resolution 2560x1440, 144Hz Gsync monitor, fps 70-144.