I'm not sure Tactics is canon - and Van Buren was never finished.
Tactics is considered semi-canon - elements that did not contradict the original games are more or less canon.
Tactics doesn't necessarily matter if it's canon or not. It stretched across a huge range but barely touched on anything along the way. Most of it was spent in military bases, mutant strongholds, or raider camps, not actual civilization. The BOS bunkers themselves are about the only locations that would need to persist to other games.
Not true, there were quite a few towns:
http://fallout.wikia.com/wiki/Kansas_City
http://fallout.wikia.com/wiki/Macomb
http://fallout.wikia.com/wiki/Quincy
http://fallout.wikia.com/wiki/Springfield
http://fallout.wikia.com/wiki/Junction_City
http://fallout.wikia.com/wiki/Cold_Water
And tribal villages:
http://fallout.wikia.com/wiki/Dirt_Haven
http://fallout.wikia.com/wiki/Brahmin_Wood
http://fallout.wikia.com/wiki/Peoria