Tight loop latency test. What am I looking at?

Running a Ryzen 2700x on a rog strix 470x board under win10 with a soon-to-be-replaced GTX760 vidcard. I've been dealing with strange pauses which are systemwide. You notice it first when the mouse stops responding for 1/4 second at a time or so. It quickly becomes unmanageable, and the whole system lags more often than it doesn't. This happens more quickly when FSX is running, but happens when it's not as well, so I suspect it's not an issue with the flight sim side.

I am seeing red numbers in the tight loop latency test (Resplendence LatencyMon in-depth) on several cores. Right now they are all between 222 and 224μs with the exception of core 0 which is at 90. I'm pretty comfortable with computers but not on this level. I know enough to know that red numbers are probably bad, though. ;)

Extrapolating from which numbers are red and which are black, I'm guessing that sub 100μs is good, and more than that is bad. But I have no idea how to bring the numbers down.

I have disabled the intel stuff that was still running from the old i5 install, but that doesn't seem to have changed the latency problem.

I'm thinking I may have to run the fresh-install recovery (win10), but for obvious reasons I'd like to make that my last resort if there's something else I can do.

So my questions are: What does a >200μs core latency indicate, and if it's problematic, how can I fix it? And why does core0 consistently stay around 90 while every other core is over 220?

Also, when I installed the drivers for the motherboard, they automatically overclocked the processor by 10%, so I'm theoretically running at 4.1ghz -- Should I throttle that back to the advertised 3.7ghz?

All drivers are up to date.

Any other tips for reducing overall system lag would be helpful. I'm getting tired of getting halfway through takeoff and suddenly dropping to about 30 frames per minute. (yes I know for FSX Intel would have been more ideal, but I'm planning a p3d upgrade, and I do other gaming on the system, so the Ryzen was a better fit, assuming I can get rid of these stutters).