[dirka_dirka]

i havent looked yet, but assuming l4d2 follows l4d1:
sm_cvar director_pain_pill_density 2
wont work on most (if any) maps because that cvar (and all density cvars) are defined in each map. you need to set an override cvar first - which overrides every spawnable object to use the same generic game settings (usually results in massive spawning of items on some maps).

either that or try using stripper to modify the painpill density for each map.

some of the other cvars might also be setup within each map, doing a stripper dump will tell you.

how do you know:
sm_cvar z_spawn_mobs_behind_chance 50
isnt working? have you run a statistical analysis?