Reply to Syncing a S4 and an other controller together ?

Hi guys
A friend and myself would like to play together, so I would like to sync my S4 and his controller (reloop digital jockey 2 master edition).
We are both going to use our own laptop (2 macbook pro, one with TP2 and an other with TPS2) with our own controller.
The problem is that I'have only one pair of speakers (Studiophiles AV 40 M-Audio).
So here are my questions :
I guess that the best would be to use one controller as salve and an other as master. So what should we connect together : the controllers via a midi DIN cable or the macbook pro via an ethernet cable ?
Then the other problem is the audio output. Following the physical connection, I would like to plug his reloop digital jockey 2 master edition in my midi thru input of the S4 in order to send our mixed music on my pair of speakers.
Do you this is possible ?
Also like this what is going to happen in Traktor ? Each of us will be limited to control 2 decks no ? And concerning the pre-listen and the waveforms : will I be able to hear his music through my cans connected on my S4 and will I see his waveforms on my macbook ?
Thank you for all yours answers and sorry for my little knowledge in the midi syncing domain