Radzig didn’t own Skalitz. It was the Kings silver mine, and he was governing it at the Kings request. According to Warhorse, he was originally a yeoman, which is a non-noble freeman. At some point he was knighted (Ritter in the HRE), which would have conferred a Knight’s Fie, a plot of land that could be anywhere from 1000 to 5000 acres depending upon quality. For reference, 1000 acres is around a quarter of the entire KC:D map. Given the dense forestry in this region, a Ritter might have ruled over 1/2 of the land. If Radzig retains these lands, they could indeed be inherited by Henry, should Radzig formally recognize him as his heir.
However, after the events of this game, Radzig becomes the Burgrave of Vyserhad, an important section of Prague. Burgravates were often the size of counties, or of particularly valuable urban areas, and conferred the rank of Count, but were generally not inheritable. I don’t know if he becomes unlanded during this point by losing his Knight’s Fie, but he does apparently become a robber knight, and becoming unlanded might explain that. If he does lose his Fie, then Henry is out of luck on the heritable front.
Like a Burgrave, an Amtmann in the HRE (Bailiff is the closest English equivalent term) was more or less an administrative title equivalent to a noble title - basically a viceroyalty. Henry, with Pribyslavitz, is becoming an Amtmann, which is the rough equivalent of an Edler in the HRE. They were expected to administer the area. This includes ruling on cases involving justice, collecting taxes, and organizing lawkeeping and defense of the area.
Not sure why you’re against Henry being allowed to do such a thing. These titles were given out precisely to take administrative burden off the plate of the higher level lords who owned the land, and Robard has better things to do than coordinate defenses at some tiny settlement. Divish certainly has better things to do than roll up there every couple days to hear the complaints about who owns which pig.