Midi mapping is easy, press the midi learn button in ableton - click on what you want to map, then move the knob/press the button that you want to map something too.
Yeah i use my VCI-100 for smartmixing - i use the gain knobs on the unit to control the smart-high and smart-low knobs. I then use 2 buttons below them to control which deck is being sidechained by the other deck for the 2 different frequency ranges. I moved the gains to the small black knob, i use the monitor volume knob on my soundcard to control my headphone volume and i do not use a Cue/Master mix knob at all.
The frequency splitter knob i have mapped to one of the 3 little black knobs on the top right of the unit as that does not get touched as much as the low-amount or high-amount compression knobs.
You need to make sure that your Traktor TSI doesnt have these knobs/buttons mapped to anything or you will have stuff happening in both programs at the same time which isnt cool