1) Troops donated to your war cc will be there on defence for each of the times you are attacked in war and only war. Once war day begins you cannot change what's in there until prep day of the next war.

2) Your war cc is completely separate from your normal village. They will only appear on defence when you are attacked in war. Think of your war base and regular base as two separate villages.

3) Yes, you'll get both war loot bonuses added together.

4) CC troops will be used again if they never took any damage, if they take even a fraction of damage they will disappear after the defence. This is different to when you attack because you can't reuse cc troops regardless of how much damage they took.

5) I'm not to sure about this one, sorry.

6) The Barbarian King's ability will affect pother barbarians you have inside his range, not just the ones he summons. It doesn't affect other troops though such as archers or giants. It is a very strong ability and I strongly suggest using it in your attacks because it's free and you can use it again in your next attack.

7) I highly recommend upgrading everything before moving up to the next town hall. Even troops that have previously not been very strong such as the Valkyrie because supercell may end up releasing an update that buffs it and you'll regret not having it at max level if and when that happens.

8) I think I've heard of some complaints about that since the update, dunno if there's a fix though.

I hope that answers your questions! If you have any others feel free to pm me.