I think both of your problems could be changed inside the UTPawn.uc or in YourPawn.uc
Jump inside the UTPawn.uc scroll all the way down to the DefaultProps block and search for those lines:
Here you can change the SpawnSound, you could either point it to a non existing package (you will see a warning after compile) or replace it with a silent audio file.
Scroll up a little bit and look for:
You have to play around with it because im not sure if one of those lines will do the trick but at least you know where to search for spawning fx.
Hope it helps