This is a problem with the way you have your mixer connected to the audio inputs of your computer or sound card. You are feeding everything coming into your mixer back into the computer, so Logic Audio is re-recording it. Let's say, for example, that you decide to connect Aux 1 Out to the left input of your computer, and Aux 2 Out to the right input. Now you can control which mixer channels will send to the computer inputs, by only turning up the Aux sends for those channels. See the documentation for your mixer for more specific information on how to connect it to a recording device.
All tracks are mixed to one track.
Nevertheless, my keyboard does not load this file. Export MIDI File saves single sequences as Format 0 in the preferences. Save the Standard MIDI File to a DOS-formatted disk. Select a MIDI track in Logic to record to. Bring up whatever menus are needed to access the sysex bulk dump parameters on the device.