Nitro X,
Ah, finally!

Ok, first you need to remove any variables or hinderances which could affect the result at the target.
This means, among other things, don't do your testing in gale force winds!
Wait for a better day.

Now here are a few things to try.
1....Make certain that you are sighting the rifle with the forsight bead right down in the rearsight vee.
I mean you need to "lock into" these guns when you shoot and a small error in positioning the bead can make a large difference at the target.
Also some doubles are sighted so that a six o'clock hold of the bead on a round bullseye will impact in the bullseye center.

2....If your rifle is shooting "apart" with the right barrel hitting the target to the right of point of aim and the left barrel shooting to the left, this usually means the velocity is too slow.
Also too slow velocity can make the rifle shoot high.
Try increasing the load 1 grain at a time and see if things improve.
I think 2100 fps is too slow for that cartridge in 24 inch barrels.
Another 50 fps might make a big difference regarding bringing the two barrel groups together and also lowering the point of impact.
As others said, don't change the sights yet.

3....Primers. Question......Is the rifle hard to open as a result of the striker dragback on the primer cups, or does it open easily and is just leaving a mark on them?
My point here is that so long as the dragback is not making the gun hard to open, do not worry about it at this stage.
This problem may improve as you increase the velocity and pressure of the load.

The reason that boxer primers can have dragback problems is that they are smaller in diameter than the berdan type and this results in a stiffer cup which is less ready to yeild to the striker as the gun is opened.

"Lifting" the rear sight will actually RAISE the point of impact and make things worse.

I think you need to GRADUALLY increase the load towards 2150 fps and shoot the rifle at 100 yards on a good day.

Also as Mac has advised, it is much better to use a seperate target for each barrel and this helps to easily determine which hole came from which barrel.

Best of luck.