Hi Kevin,
I’m always reluctant to point things out to you because you are clearly playing in a different league. 
But I don’t understand your point about grouping - did you not mean exif grouping? That would be one click for all cameras grouped. You can also select many, like Jennifer has pointed out, and change whatever value you want for all of them.
About the 2500 - it might be worth a try, maybe there is some little ■■■■■ in the code somewhere.
I see your point about the hard won alignment. Although your experiments prove (in my view) that it is somehow tied to the mesh geometry, since it seems to disappear when you simplify it to a high degree. So the intersecting faces do seem like a possibility for the source of the error. Have you tried cutting random parts of the mesh away to narrow the spot down? Maybe downscaling images for texturing helps reduce calculation times for this.
Sometimes it can be faster to talk about such things in person. If you think I might be able to get you any further, feel free to call me - you should be able to find my details in google with my name…