You can get Ballistic Armor by going to the top floor and jumping off the edge nearest the doorway. Go through there and the armor will be on the right-hand side. There are extra rockets to the left.
The Impulse Rifle kills in one shot anywhere on the body. To get it, go to the top floor using the middle lift and jump off the end nearest the Impulse Rifle. You should just make it. Quickly jump off there because your enemies can easily see you.