Maybe I'm not far enough in the game to really know about the gates but earlier today I was riding out in the middle of nowhere in the mountain area in the north east part of the map. Fending off some imps and wolves as the usual things, while I'm looking for out of the way crypts or caves or whatever I can find and then I look farther up the hill and I see a gate to oblivion just sitting in the middle of nowhere. It just caught me by surprise I went out looking for caves and found another portal.
How many gates are open and how many can I find at the moment? I've closed the one at kvatch but have gone no further in the story and I've seen this one.
the stone useless? Ever clicked on it??? You enchant stuff.
On the gates not being there - They open gradually, not straight away. The map is simply saying there is a site for an Oblivion gate there, and a gate will appear in the future.
On Valenwood - You can go pretty much as the map shows into Valenwood so yes, gates can appear there. Of course there is no Settlements.