Glad you're enjoying it!
As you note, I left them ambiguous on purpose so that everyone can make the Wenderweald their own. How you've interpreted it is very cool and highly encouraged.
I'm happy to share my interpretation of them. These aren't meant to be canon; just how it went for me.
In my game, Thurn was the champion of the first and only successful crusade in the Wenderweald. He built his citadel 60 years ago to consolidate his hold on the region. With no heir, though, his hold on the barony collapsed after his death. The citadel itself is located 12 miles north of Gideon's Reach to watch the pass between the swamplands and reaches.
Knight of the Corpse Trials took place exactly where you put yours: just south of Crescentcroft. The Leshi there wandered south after consuming all of the loggers.