Thus far, there are a lot of clues pertaining to the problem. It seems evident that the bent extractor problem is due to forcefully opening the gun with a shell stuck in the left chamber. The barrels were a pretty effective lever. Archimedes would understand. Were both barrels fired, or just the left? As Ted says, the extractor can probably be straightened.
Since Gunter has already shortened the firing pins, I'd like to assume a gunsmith of his repute at least checked for correct protrusion. Unfortunately, some gunsmiths do not test fire with live ammo. The old German gunsmith who had a shop near my parent's house had a hole in the floor of his shop so he could test fire guns into a drum of sand in the basement. The first time I saw (and heard) that, he fired a .30-06 into the hole without any warning. It certainly got my attention. The Federal factory loads should be sized to fit any correct chamber dimensions, so the chamber may be undersized (which would be evident when loading), or rough from reamer marks, or pitted. The empty stuck for a reason. Tearing part of the rim off is a real big clue.
You told the Nutty Professor that the opening force was essentially the same whether the gun was loaded or not. Then you said it was somewhat easier to open after Gunter worked on it, but still fairly stiff. Did you mention to him what Kutter said about checking the spring, and checking to see if the spanner nut on the top lever shaft was over-tightened? Those things would account for the stiff top lever. I think Kutter has demonstrated that he is very knowledgeable, so his advice is worthy of attention.
I am also curious if the opening force is somewhat less once the gun is cocked. There isn't a whole lot going on to check. Opening force on the empty gun involves some friction at the knuckle and hinge pin (hence the obsession some have with hinge pin grease), cocking the hammers (cocking rods and compressing main springs), and moving the extractor outward (which you already said moved freely prior to bending it). Adding shells to the equation adds the friction or force to extract the empties, and possible firing pin drag, (which has supposedly been professionally addressed). A loaded gun can also be more difficult to open and close if the critical rim recess (headspace) dimension is a tiny bit too shallow, allowing the case heads to drag on the breech face.
Finally, you might need a gunsmith who has a hole in the floor and a drum of sand in the basement. Bring ear plugs.
