I’m not sure I understood properly but not clear for me if you need only 4 channels output from the LP-16 why you want to use 14 track song instead of 4 tracks.
Anyhow there are couple way to do this.
1. Set up the mix in the uTool for the 12 track for the sound guy, mute the clicktracks in the uTool mixer, export the song. Use the headphones output for the soundguy, but this will be a two channel mono mix, because the LP-16 have no panorama settings in the uTool mixer.
2. Make a stereo downmix in your DAW, then export the stereo song as two channel mono file (L and R channels) use this two mono channel in the uTool on your output 1-2 and the clicktrack on output 3-4.
3. Use the previous method to create a proper stereo downmix in your DAW, use this downmix on the CH15-16. In this case you can have a 14 track as you have before in your original setup, but you’ll have a stereo downmix on the CH15-16