Part 1 is correct. If AutoDJ is casting to shoutcast, SC will not allow any other connections. YOu need to boot the AutoDJ to connect directly to shoutcast from virtualDJ.
Part2: Disconnecting, Reconnecting usually has something to do with shoutcast not accepting the stream codec. I'm not sure how your virtual DJ software is streaming to shoutcast, but it usually accepts aac or mp3-lame streams. I would recommend turning on debug mode for shoutcast to see exactly why it is disconnecting the encoder from VDJ.
Alternatively, you can look into the liquidsoap documentation on how to setup stream relaying.