Make sure you have the latest version of Kontakt. It works very well on OS X, but older versions didn't (although they were fine on XP). And I don't know whether the latest version has fixed the OS 9 problems; it may have, but older versions worked very poorly, especially when you're streaming.
I'd be very conservative with how much you try to run when you're playing live. Kontakt lets you set a voice limit for each instrument it has loaded, and I'd recommend setting the minimum you can get away with before the cut off voices are heard.
I don't think patch changes are the way to do it. You're going to have all the sounds you need loaded up anyway, so I'd just put them on separate MIDI channels.
Also, you need to play with the settings in Kontakt to maximize its performance. The DFD settings I use are 256 voices, 192 somethings, and 384 something elses. (I forget what they are!)
And download the latest DFD extension.