There is no third wall - but each race is getting stand alone fortifications - sort of as a third wall layer. Although Orcs and Elves are getting the most here - as we judged their defences too weak.
At this point no - no visual indicator - but that's something we hope to add in the future. Mad I hear you - we need something like that for the central building.
We will be expanding number of armies shortly - but not the homeland or army pop cap. Until some point in the future that we get new path funding in it would just lag too much