Hi there! We're working on a detailed write-up of the specific GE entities. In the mean time you can feel free to ask questions here.
Regarding ladders: Ladders are actually point-based in our game, meaning you need to make a point entity called func_useableladder. What this will do is create two boxes that are initially overlapping eachother. Simply click on the origin of the box in the 2D view and drag it to where you want to define the ladder. It is also important to make another point entity called info_ladderdismount. This tells the ladder where the player can mount/dismount from the ladder.
This is how it should look in Hammer (the yellow boxes are the func_useableladder while the white boxes are the dismount points)
Please note: Ladders in the Source engine can be awkward to interact with, and they are only used where they are absolutely needed in our official maps. If you can design your map to traverse heights by ramps, stairs, an elevator or even by stacking props, I'd rather suggest that.
Regarding weapon spawns: You are correct. The weapon slot value for the spawner in Hammer will correspond to the weapon listing in each set, hence why the 8 spawn using the Silver Shooters loadout gave you a rocket launcher.