You're using OXCE+, right? Most of this is in there:
1: Make armor only from loot item that is gained from a mission that happens only once, workaround, but it does work.
2: OXCE - damageAlter tag on item, ToArmor can be negative I think to repair armor, set ToHealth to 0 if you don't want it to hurt!
3: I think just use a different article type number in the ruleset? Check the ruleset reference on Ufopaedia.org
4: Done recently in OXCE+, choose many item sounds randomly from lists, just like death sounds
5: Not sure if it's possible
6: Same as 2, ToMorale, ToTime, ToHealth being negative can buff units, see Piratez' battle flag