I'm sure the answer to these exists somewhere on this sub and I'm just searching the wrong terms, but would appreciate guidance...

I have access to a Behringer X32 (RACK), and my band would like to use it to record some tracks. I've managed to navigate the whole multitrack recording thing without any difficulty, but I'm having a couple of issues with playback.

First, I can't seem to figure out how to make my computer audio route through the mixer. If I select X-USB as the output in garageband, I get silence on playback. I'm guessing there's a routing setting on the mixer that I need to be changing, but I do not know what it is. Thoughts?

Second, when I've played some test recordings through my MacBook, it's... really really quiet, even with all volumes maxed. My standard speaking voice recorded a handspan from the mic is almost completely inaudible. Energetic singing with the mic resting on my chin is at most pianissimo. Is there a way to correct this? I know when I record on the built in mic, my speaking volume is roughly what I get on playback, so I'm confused by these ultra-quiet recordings.