We agree that your point a) is likely a memory leak or bug in the memory management of MSFS since it tends to over-commit memory under heavy loads on my PC. Other programs handle this much better.
Your addendum that memory use is dynamic is of course important. I should have noted that in my summary. But it was not my intention to ignore that fact in any way.
When I fly in MSFS I see a variance of about 4 GB over complex scenery. Meaning it frees up some memory in the cruise portion of my flight but as soon as I get near the destination the usage and commit surge up again, leading to a situation where there is no more VAS available and the sim crashes.
So arguably the problem is not only that the simulator is unable to free up memory in time, but it also commits too much of it at times, which can lead to a CTD, sometimes even without error code, making it necessary to dig into the event logs of Windows.
The only mitigation strategy that worked for me was tuning down the detail of the procedurally generated entities like buildings and trees and reducing the size of shadow maps.
That resolved 90% of micro stutters and enabled me to finish 75-90% of my flights.
I will check out the tool you mentioned, but seeing how many private bytes Flight Simulator is demanding, I doubt it would have much of an effect.
Edit:
@OAPJRG
Does RamMap use
%windir%\system32\rundll32.exe advapi32.dll,ProcessIdleTasks
or does it have some added functionality to clear the RAM?