Oh wow, good catch on Red Leader! I swear, I keep coming across typos, although I suppose it's inevitable when you end up writing a book this size.
Yep, the base cost of an armature is 2 Profit, plus Scale #, plus the number of edges, minus the number of flaws. I suppose there's no technical limit to the Scale of armatures rules-as-written at the moment, but my notional limit is essentially craft-scale, if you can muster that much Profit (and have the space within your existing craft to build such an armature, of course). This is definitely something I want to write into the book, or at least delineate my thinking on - remember, you're using the light-fab to build the armature, and the light-fab is embedded within the craft, so the craft's Scale itself limits the size of object you can print using it.
The scale of a war-shell is Scale 1 - remember, the maximum Scale of an object contained within another object is the Scale # of the other object -1, so things like war-shells, small fighters, etc. are generally going to be around Scale 1 so they can contain Scale 0 human meat-bags.
Hope that answers your questions, and good luck with the game! Let me know how it goes :)