The split screen should be correct. Make sure you eye is centered on the viewfinder.
The ground glass image on the other hand is subject to errors based on your eyesight.
That's why they make diopters (corrective lenses) for the viewfinder. These only affect the GG image, not the split screen.
The subject of focus shift is rather contentious, and has been discussed ad nauseum.
Some people think it always happens; some think it never happens; many are in between or undecided.
There's a very simple test for your lenses.
Set the camera on a tripod and a good focus target at an angle across the field of view.
Focus on the middle of the target using the split screen.
Take a series of photos at all available apertures, controlling exposure with shutter speed.
You could do this test initially at 5 (or 10) feet, then repeat at twice and four times that distance.
I've never encountered a Nikon camera nor a user thereof that required that kind of correction.