what you can do is run seperate tracks out of your mac and into the desk for mixing and summing, but then you are relying on extremely good converters and that is extremely expensive. And you don't want that, do you?
For cheap control of your DAW you could try the behringer midi controllers. might be alrite epsecially as no audio is passing through it

but I don't know the resolution of the faders (and consequently how accurate your fader movements will be replicated)
Why do yo uwanna waste money anyways - what's your goal?