
The app
I developed the map but I'm not the only one that worked on it!
Chris was the illustrator who painted this huge map in watercolor, it was then improved with some digital painting.
Next, I developed the system that allows us to navigate in the map with google-maps-like features (thanks to LeafletJS library). I also developed the directions calculation system based on a cartographer algorithm (Dijkstra's algorithm, to be more precise).
And finally, Iris (co-coordinator and one of the main writers on Esteren), Evolena and Ethilon (two great members of the Esteren community) worked very hard to list all routes and markers on Esteren's map (the work is HUGE and stored in this file, just for you to see the amount of work behind this

Evolena and Ethilon also had to use an administration panel of my creation to update the online map and position the markers precisely, draw the routes and zones. Again, lot of work!
Distances
Obviously, when we realized that calculating directions in this app could also include time travel and distance calculation, we wanted to test more things in this feature, but we faced the same problem as you: distances "realityness".
Of course we had discussed a long time, internally, about how we can make a "real" map (the online map behaves like any "real" map, so distances are very precise) concord with the "fictional" map that was created?
Indeed the different scenarios implied a specific time travel between Melwan and Terkhên, for example. The problem is that the app showed us "how unreal" this was.
We had to specify a scale for the map, and we decided that the distance between the Wreckers (south-west) and the Pass of Gaos-Bodhar (north-east) was about 1000km.
With this scale, I can apply a ratio on the default map and calculate distances very accurately, thanks to computer calculation.
Melwan and Dearg were told to be about one day and more, and in fine the app states for five hours, which is quite less. And all other distances are like that.
We decided that we would try to adapt new scenarios and books to what the software tells us, but sometimes we will need to accept that distances are accurate nowhere :p