Howdy Josh,
Is this the stuff?
http://7.62x54r.net/MosinID/MosinAmmo011.htm
http://www.mosinnagant.net/i3tro4.asp
I would share your healthy skepticism about claims that it is non-corrosive.
I would strongly counsel that it be treated as corrosive.
In any case, it will be Berdan primed, steel cased and not reloadable. I don't know if you are thinking of reloading for the cartridge any time soon (I dimly recall you were debating it since ammo prices have been rising so steeply...), but if so, save the brass Boxer primed cases.
The link on the "bxn" 1963 ammo above suggests that many Mosin shooters find they have "sticky bolt" syndrome with the lacquered cartridge case. After your methodical tests with the USSR stuff, I guess I'd check about the overall case length and what-not.
As to it being "AP," the claim is made that it has a mild steel core. You might see if the bullet attracts a magnet. My suggestion would be to buy a small amount, shoot it, and see what you think before you get a huge lot of it.
As far as the neck cracks on your 1986 USSR fodder, it looks like a neck case crack is not too dangerous because the rest of the case body seals the chamber to the rear. But the bulge case head seems like it is potentially not good.
best, --d.