1) It is on purpose, the mod is foccused on multiplayer so you have the load all the units manually in.
2) Any normal firefighter can do it.
Annyways: On-Topic:
Also, Virruses and Trojans are found with keywords, sometimes it can give a false alarm, assuming you downloaded it from a official source, it doesnt have a virus.
With the firemen, click the Enter ladder then the ladder that should work.
It would be very annoying if you hover over the ladder and it insta goes to ladder so you have to slick the button.