I don’t quite understand your second problem, but your first problem is that you have release turned all the way up on the Amp. This means the volume will stay open forever. If you put the release down, the sound will fade away once the triggers stop. You could place a trig that is the length of your sequence, (32 steps or whatever) and then have full sustain, no release. Meaning when you mute that track, the sound will stop instantly. This is because the A4’s muting works by turning off the track’s triggers which lets any existing sound trail off naturally, instead of the OT’s mute which just silences the whole track.

Hope that helps.