1: When you get the choice of awakening victory to go for, choose the one that you are furthest from completing. I have always completed at least one or two of the conditions by the time I get to chose so the only way to continue is to choose the other one.
2: I assume you can't see all the map; as far as I know if they have zero territories they are eliminated, so if they are not they have somewhere you haven't seen yet.
3: Forcing a truce is only possible (afaik) when you don't have an overwhelming war score in your favour. Aspects are easy to deal with if you make sure you are on the winning side in battles.
Using Necro I generally have hundreds of single units roaming around all over the map (because who cares if they die) but before you go to war with Aspects consolidate everything so that you only have armies with 2.5k to 6k power and keep two armies near each other (6k armies can handle anything on their own); Aspects will never win a battle and your battle score will be several thousand compared to their double figures; they will not be able to force anything!
Edit: I was actually wrong about Aspects forcing a truce; with a war score of around 40 to my 4k they were still somehow able to force a truce.
The actual mechanics of it are not well explained (afaik) and it seems pretty stupid that truce can be forced in such circumstances and nothing can be done about it. What is the point of having war if a civ can just stop it and you can't do anything about it. Nevertheless even with the ability to force truce for 7 turns I don't believe that it is long enough to stop you from preventing other civ reaching their victory conditions before you have time to exterminate them.

Conquest is currently the most tedious win condition. The main problem is that you can raze every city of an enemy empire, if they still have a hero running around and enough influence to build a camp, they can just place a new city somewhere else. Which happens quite often.
There is agood reason why Civ only asks you to get their capital, it's just too tedious to remove every single city of every single player.

The Aspects are broken either don't add them to the game, kill them on site, or keep under 5 territories. Once they get enough big enough, you cant kill them. I was forced to peace out and my main army left to get a curiosity in a obscure plateau then it was trapped there for almost the rest of the game. By the time I freed them my only enemy left was the un-fightable aspects. Necrophage playthrough ruined :( Same thing happened again on 8 player endless with the Lords. I caught it early and they only had enough influence to stop war 3 times as I contained and hunted them for almost 100 turns to conquest victory. 21 turns wasted yet again.

2. yes i had this too. wiped out all of their cities (with very little fog of war and clear sight of the area that became a settlement) and moved on to the next faction not realising they weren't knocked out. 10 turns later they had a new cities. I'm guessing you have to make sure they don't have any settlers left hanging around.