Terebi

Well, you were right. I think the problem was actually ram now. Not bad ram, but I had (foolishly I know) mixed the original 4gb chip with a 16gb addon.  In retrospect I know ram should be matched, i was just being dumb.  With either chip (but not both) the system is fine. 
 
The weird part is still the pattern of instability though. Only that overnight crash.  If the ram was causing problems, I would expect the instability to be at times of heaviest usage. 

The issue ended up being that I enabled cstates in my bios to reduce power draw and cpu temps. But apparently that caused frequent crashes.   Further information was that CPU would spike up and stay spiked for 30-60 minutes prior to a crash, and that already-open connections (plex, tautilli, dashboard, etc) worked, but if you closed any of them and tried to re-open, it would not connect. 
 
Since disabling cstates I have been stable