1 Not sure. In my previous game, I'd completed the orc wall and stocked it with some 25 units before the quest even showed up, and the quest remained open despite full storage. Possibly the quest will complete only after attack protection runs out?
2 You mean walls around green shimmering stuff, or around a campsite with bodies?
Some maps have healing wells on them, and the flags you're seeing may be your units' destination flag.
... also some oger groups have picknick grounds that look a bit like that. If your troops start dying fast, click "World Map" to escape :-)
3 Depends on your race:
Humans can build a minecart and just park that near the mine/forest. Workers will drop off stuff there.
Humans also have a building that serves as a drop-off point (barn or shed I think).
Elves magically teleport resources so no need.
Orcs can build huts, each one is a valid drop-off point if I remember right.
4 Note sure, but you might want to send an army to a dwarven area, set up a tent camp (so bring some gold) and see if you can recruit anything.
(I tried Ssilistra but the camp couldn't recrit anything, and I fled when I saw a dragon)