Sorry, as you only said CPU 55% usage I didn’t think you checked per core, my bad.
One of the problem we have monitoring MSFS are the CPU spikes, often due to the instrument display panels. Problem come from the granularity of monitoring tool (often from 0,5 to 2 seconds) which don’t catch a rapid spike so you may think you have E.g. 80% on one core where in fact it maximized to 100%. In scenario where changing any graphical settings (even lowering Renderscale to 30% monitor or VR) your FPS don’t really change are often due to CPU.
I can only maintain my 45fps ASW OFF with plane with steam gauge, and the most FPS friendly plane I use is the Cri-cri where I have 45fps nearly everywhere.
Also, only ASW 1.0 is managed in MSFS and we have a thread to vote to implement ASW 2.0, that will make lower refresh rate more comfortable:
The good thing is MSFS part of Devs said during last Dev Blog they don’t fly on monitor, only in VR, so we have some hope they still optimize the Sim. In any case any optimization on the main engine will benefit for all kind of sessions 
Edit : Oh and if you want to really fly at your native headset fps and with supersampling at more than 150% on ultra settings, I suggest Aerofly FS2. I clean my VR eyes with this Sim (and also Asseto Corsa and Automobilista 2) 