Update:
I locked in my game version to 1.2.1 and started a new game. IT WORKS!
I installed a few mods, mostly that make fixes to the game that taleworlds hasn't gotten to, and have had no problems. I had a few crashes that were related to a specific mod, but it was easy to track down and fix because it was repeatable. There are still glitches related to sporadic low frame rates, and people turning partially invisible or naked during the initial clash of a fight but not 1 game related crash. This seems to support my theory that the updates were not totally save game compatible. I will definitely not be updating the game again until I want to start a new game.