There's a lot of things Espenson said in an interview for Caprica that are contradicted in this map such as one colony being a debris field with an atmosphere straddled between two other ones. Probably dropped because the science adviser.
Since the map is dated to probably just post Caprica, the 50 billion figure is probably a post-war boom.
As for the armistice line, I figured it's within a few light years. A few years back someone did up where the Colonies were based on the lagoon nebula's appearance, which would make the Colonies and Kobol in a rimward line from Earth. Based on the constellations
Cylon Earth
and Earth are probably not too far and New Caprica is on a beeline from Kobol towards the Lagoon/Ionian (whatever that is supposed to be).
Space is pretty damn big, so in the end it doesn't matter but it's probably any direction but Kobol.
So probably the overall fan map on battlestar wiki is pretty accurate:
http://media.battlestarwiki.org/images/0/0a/Locations_in_BSG_galaxy.jpg