The rods you listed will work with the KK500 buttplate and stock. They are no different dimensionally aside from the length and attach to the carrier in the same manner. I've actually tried swapping buttplate between my KK500 and KG400 air rifle just to try certain things out.
The firing pin on the KK500 is considerably thicker than that on an Anschutz 19xx/20xx. So it should be stronger and less prone to breakage. But I still wouldn't do a lot of dry firing without either an empty case or a snap cap.
And no firing pin should be hitting the breach face without a round in there. Mine does not, and if yours does the firing pin is too long.
I use drywall anchors like the ones in the link below. These are a low cost alternative to snap caps specifically made for firearms. https://hdsupplysolutions.com/shop/p/-4 ... 00-p740865