Taking into account #4 it seems that the game itself already takes care of not allowing the 0 value. If it does, it seems like 0 is not an acceptable value.
Excuse me if I am wrong but I would compare it to the CS 1.6 cl_bob* cvars and with regard to them any other values different from default was not allowed.
try to enter "cl_bob_lower_amt". You'll see:
"cl_bob_lower_amt" = "5.000000" ( def. "21" ) min. 5.000000 max. 30.000000 client archive - The amount the viewmodel lowers when running
We are talking about "0" ?
I had problem with dust in the past, after 5-10 minutes of play, my fps was dropped to 15 instead of 100-150 in every game. My VGA burns like hell, because cooler did worked poorly due to dust. My English is bad, but i hope you are understand me.