I think you dont need an injecter kext for your graphics card to boot the installation, if its supported by nvidia drivers it will boot though without acceleration (CI/QE). I might be wrong about this though.
You also need voodoo kernel for i7 I think, for the USB Drive it will be easy to use it, you just have to put the mach_kernel.voodoo in the USB drive's root and edit the chameleon's com.apple.Boot.plist to use it instead of mach_kernel.
I'm not sure about booting the installed system from the USB though, I dont know if chameleon uses the kernel from the USB drive or from the partition, if the latter its true you would need to manually copy the kernel file there replacing mach_kernel, if the former its true maybe you need to specify the kernel file using a specific device (like (hd0,1)/mach_kernel.voodoo).