I haven't noticed this problem? If its truly related to func_breakable, use a func_wall_toggle and some env_shooters. If its a problem with func_water, either dont use it (just solid water), or use a really REALLY dark texture for the water.
Random events are done using the random properties of a laser, as on VERC
http://collective.valve-erc.com/index.php?doc=1045094934-21558900Anything beyond the sky texture is null, therefore the bullets hit this and create sparks etc. As it happens in every map ever, I wouldnt worry too much about it
No you can't, other than creating a mod and editing the ladder sound directly.