In Kontakt each instrument loaded into the rack can have its own output (up to 16 seperate outputs per instance). Select the ouput in the instruments main panel. In Kontakt Options you can setup the desired number of mono and stereo outs. In Logic choose Kontakt as Multiple VST. On further Aux-Tracks the additional ouputs 3 and higher coming from the multiple instrument can be selected as input. Of course the aux track must use the same audio driver as the Instrument where Kontakt multiple VST is. In order to send MIDI from different MIDI tracks to the same instrument you have to create a "multi" instrument object in the environment and connect it to that instrument where Kontakt is plugged in. For your MIDI tracks you will be able to select this multi then, each MIDI track sending on its own MIDI channel.