Quick first responses ...
Seignory - this has a good archaic 'feel' to it ... keep it, please !
"Tonder bought 10 stone for 120 pounds to Neumunster." - suggested "Tonder bought 10 stone for 120 pounds from Neumunster." - possibly better as "Tonder bought 10 Stone, paid 120 Pounds to Neumunster." ... the capitalisation of Stone and Pounds indicates that those terms have specific meaning in *this* world ... again, it maintains the more formal/archaic tone/'feel' ...
"Right of Way" in English means that *anyone* may cross that land or path freely - the owner of the path is not allowed to close that Right of Way ...
"Right of Passage" sounds clumsy - unless Garik is confusing "Rite of Passage" which means a ritual used when a person passes from one human condition to another, perhaps by promotion - as the Rite of Passage when becoming an adult ...
"Free Passage" is the military/diplomatic term in English when one permits a specified non-owner to cross one's lands ... one grants that non-owner Free Passage over/through the lands ...
Do these help ?