Your Trigger
Regarding the trigger, strange things can occur internally in any of these old fellas we're so wrapped up with. I haven't had a Fox apart for thirty years, but as I recall, they come apart fairly easily. If I had a trigger that bad, I'd want to disassemble the receiver enough to remove the butt, reassemble the receiver and then carefully examine both components. On the wood, I'd look for splits, cracks, deteriorated wood, etc. On the receiver, other than something easy to spot, I'd cock it, pull the triggers and see what I could see. A special little thing I'd do is to try to tighten both rear tang screws to the same level of tension I found them in before disassembly. Then I'd vary that tension and continue testing. Don't forget the safety, either. Chances are along the way you'll discover why your rear trigger is so contrary and have a leg up on fixing it. This little protocol also provides a chance for thorough cleaning.
The DGJ Articles
Got what I expected out of them. If their titles had been "The Fox Shotgun - 101", I would have expected more mechanical and "how-it-functions" type info. But they weren't. What they gave me was more of the fine-grit type info on the Sterlingworth Fox I crave, as a fairly advanced Sterlingworth admirer. The articles met my specs.
Barrel Extension - Frame Join Point
Never noticed this before. Wonder if there were any subtle dimensional differences in barrel width/height, or the same for the receiver, among the three. Is the wider radius deeper, along with being wider? Is the rib on the 1910 model lower than on the Utica model? Maybe just some sort of production economy - don't know - but interesting.