Yes, it is my impression that she Hit Locked and Loaded to get a few weapons. Than makes it to Eastern Bay to free her Brother (and the others of course) When I try to game it out, I can not get the zombies to hit Eastern Bay, have the mallers escape, have the mallers cross back across town hit Burt's safe before Burt and the Zombies get there. I think "The Weapon" taken from a safe mentioned later is not from Burt's same safe.

The way I see it, Scratch hits Locked and Loaded. Scratch crosses town in the infancy of the zombie outbreak and hits Eastern Bay just before the Zombies get there.

I am not following the rat idea. We know a shot came from the third floor. The person may not live there. No clue about the Guard Duty / Return of Saul. No clue about Angel

What I will point out is that Ammo was at a premium in the tower. There are not a people who would have access to common supply of the tower. Indicating to me that they had their own Stash.