How and is it possible to setting shoutcast V1/V2 in PlayItLive?
SHOUTcast settings can be entered by downloading and installing the Internet Broadcast plugin from the plugin gallery on PlayIt Live. The documentation for encoder configuration can be found here: http://docs.playitsoftware.com/InternetBroadcastPlugin/encoder_configuration.html
You can adjust the volume(strictly subjective loudness) of files with MP3 gain.
Producers tend to compress sweepers and jingles more so they sound punchier. Currently there is no way to control the volume of individual tracks but I can understand your need for this. I would recommend dropping them into your favourite audio editor and reducing the volume using the Amplitude effect.
Thanks for expressing your interest in a dark version - this is something I am considering adding next year.