After a few more rounds of testing and failing to find an answer I was about to post a diatribe about how posting my load order rarely helps.
Usually because I've rarely had answer worthwhile come from that. I was going to go about how I've convinced myself that FCOM is the main problem in my load order (many spawn point corruptions) - and that Enhanced Daedric Invasion compounds the issue. I was going to go on .... blah blah blah.
Then a breakthrough - I found the offending mod. About a half a year ago or more I went on a mod merging spree - motivated by PetrusOctavainus no less - and one product of that was a mod I named 'Villages and Forts.esp' it is a merger of these mods:
-Villages & Inns-GottshawVillages 1.1Tel VallusPine Peak Lodge-forts & Hideouts-ImpeREAL Unique FortsFort Nova SadFort Novi VarosBandit HideoutsBarbarian Camp-Other-Hunting TowersWatchtower
Basically a lot of locations. And so it was the Villages mod by Martinb was the 'thing' in that area causing crashes. Now here is the main point - when I made this I had extensively went out of my way to make sure that it worked. That meant examining in tes4edit for any conflicts with other mods loaded (including TOTF), Gift of Kynareth ... and especially the UL and the patch Vorians made for the UL (renaming masters, checking in CS, etc) then testing in game by going there with characters and testing with both fast travel and running all over the place. It was work.
Well even though I had done all that and the character had been to tall those places - well now it doesn't work. No great loss - I like the village of Beram and the other mods in there, but weighed against the main quest and TOTF - I can live without the added fluff of the villages/forts. Perhaps I will reactivate again later and retest - once I've convinced myself (maybe fooled myself) that I have stability again. Or remerge them without that mod.
So long story short - my fault. I study BOSS and stay on top of every update I can so I was doubtful load order would have helped and I was right (in a sense).