How far apart things need to be would depend a lot on the transportation/communication technology and infrastructure available, and even on non-obvious things like social structures which hinder or promote travel and communication. That large inland sea with loads of spindly arms is actually a severe hindrance to breaking things up as it provides an excellent transport corridor.
I'm still in the process of reviewing scale (things like mass and density aside, inconsistencies of which i will unapologetically waive due to the reality of the worlds' mythology). in a nutshell i want a large distance between cities and settlements (a means of fomenting corruption and a 'frontier' character) of course the world was not always like this, ending up like this after a diminishing of civilisation and culture, with many ruins peppering the hinterlands between settled areas. anyway, i digress. basically i wanted this region of the map to range from subtropical in the south, to arctic circle in the north, which covers around 10 deg - 65 deg lat, which plays a large role in determining the scale. any thoughts?