1. Turn off the metronome under options/project, for both recording and playback, no ticking sound.
2, No idea on the "hishing" sound, try turning off the "hishing" button, no really you need to be more specific, that could be anything.
3. On the issue of the volume going up and down when you record vocals, are you wanting it to act like a voice over? where the musuc automatically lowers when you speak, like on a commercial? If so that is a technique called ducking, and I don't thing MC does this, it is a feature of more full programs. There is one way, to accomplish this, it will not be true ducking, but by using an volume envelope, you can physically lower and raise the volume at certain points in the track