In regards to the background noise, it almost sounds like the lack of shielding in the cable going from your baby monitor to the LineIn of the PC. The first attempt that I did with the baby monitor, I used a poor quality cable, actually I tried to use a PC microphone cable and solder it to the baby monitor. This cable did not have shielding and I experienced similar issues as you. I then removed that cable and used a proper cable like Dave_x10 used in his and then I had perfect static free and noise free communication to BVC. So with all that said, I thought that I would share my experience; so you may want to check your cable from the baby monitor and LinIn of the PC.
Good Luck.
Nate