Johnm, nice to see some real research going on!
Did you use a sample of ATF in your experiment?
If so, how is it holding up?
Interesting that you mention using mineral spirits etc as solvent additives. This is practically the same thing as a popular home-brew gun cleaning product called 'Ed's Red'.
I use this on all of my firearms, and it works great. It's actually what got me started on researching lubricants rather than just trusting the writing on the bottle.
I recently bought an old sxs shotgun, and the thing was covered in varnish from old oil (my guess is 3-in-1).
The firing pins were stuck so badly that if I had closed the gun with shells in the chambers, the protruding firing pins would have set them off. It also stunk to high heaven.
I dropped the action in a bath of ATF and barbecue lighter fluid, and the next day it was clean as a whistle and functioning normally.