First of all, welcome to the forum!
Here are the answers to your questions:-
1. I must agree with Schruaf, that the troops donated for the defensive Squad Center on Sullust, will remain throughout the war, regardless of being killed.
So even if you attack the same base three times, the same troops will come out of the SC, regardless o whether you killed them in the last attack.
2. No Armory Buffs for Defense or Offense are used in Sullust. You cannot Attack using the buffs even if you have them activated in your armory.
The only way to have the upper hand in wars is by capturing outposts. They provide a great advantage only if you capture them.
Hope this answers your questions...