Hi Swamptooth -
Yes, Forte can do all of what you're talking about...but...for your gig, I'd suggest Abelton Live.
Forte is designed to be primarily a VST/VSTi host, so you can load up a rack of samplers, trigger cues, use Scenes to re-map controllers, etc. You can even use things like EnergyXT within Forte to trigger backing tracks and sequencer patterns. But, from the way you describe your performance needs, I think Live would be a better solution. Sonar's Matrix is sort of a weak emulation of Live's capabilities, so you're already working in that manner.
As for whether Forte will do patch changes for Dim Pro and Rapture, absolutely yes. Each scene can be a separate patch, or you can load 1400 different instances of whatever synth you like and trigger each one as needed.