The Model 42 is NOT designed as a take down gun.
Removing the screws will void the warranty.
The extractor is indeed of a polymer composition, it functions just fine.
Most .410 hulls and .22 empties will simply fall free if you upend the gun.
The .22 barrel is sufficiently accurate, I get 2" groups at 50 yards with a variety of .22 ammo. Closer you shoot, the tighter the groups.
The .410 barrel is very slightly choked, 3" chambered and shoots any kind of .410 shell including slugs very well.
I would say the maximum effective range for the shot barrel is 30 yards.
The shot barrel shoots 2" lower than the .22 at 25 yards.
I learned to put the front sight in the rear sight notch for the .22 barrel and to set the bead just above the rear sight blade for the shot barrel.
Standard velocity .22s shoot lower than high velocity, this is corrected by aiming bottom of bull/target for high velocity and spot on for standard velocity shells.
I had to adjust the rear sight for windage and elevation to get everything dialed in.