The loss of air is easy to explain. The suspension is softening up with increasing hours. Virtually all new cartridges do this, that's what "break-in" means. Those who say they haven't heard a new cartridge do this, haven't been listening. I've gone through it with a dozen cartridges.
So, what to do?
First, reduce anti-skating to a bare minimum. I completely agree with other posters that excessive A/S is not needed with this cartridge. (With all respect to your friend, setting A/S with test records is nonsense, unless all you listen to is test records. Test tracks are nothing like real music tracks. Ignore them and start trusting your ears.)
Second, because the suspension is breaking in you need to start reducing VTF. Choose a dynamic, difficult-to-track passage and reduce VTF in .1g increments until you hear mis-tracking (sharp, static-like bursts at dynamic peaks). Then bump VTF back up by .1g or so. Your air and snap will come back in spades.
Image shifting is a trickier problem, but it can't be dealt with until you've optimized VTF and A/S, so fix them first. There's no magic number anyone can give you for these. You must learn to adjust by listening. There's no other way.