may the other topic is better in your case :
https://forums.flightsimulator.com/t/after-playing-a-few-hours-fps-drops-from-40-to-5fps
related to ndu discussion: the non-paged-memory usage is a little bit higher, but may after 8hours normal. At least it does not consume 99% of your RAM … so, not surpriced that ndu setting is not helpfull in your case.
EDIT: have you set a 130GIG pagefile ??