Separating and Mapping Audio Channels in Premiere CC Multi-Camera Sequence
Premiere Pro is definitely not a digital audio workstation.  Its treatment of audio is primitive at best.  I believe its paradigm (which I think is screwy, but that's my opinion) is that a multicam clip conveys one of two types of audio: the preview channel track (which you have selected as Channel 1) or audio-follows-video, which means each cut you make, the audio switches to the one channel allocated for that clip.

I know you don't want either, but I don't think there's a third way.

So, use Channel 1 as your reference clip, copy and align the audio tracks you want to deal with to the sequence containing the multicam clip, and do all your audio edit processing there, separately from your camera changes.  Good luck!