Just try it all out and see how you go with it.
You can render the Sforzando track to wav.
I think the midi was from the original audio tracks maybe using Superior Drummer 3 ? not sure what they ended up using to convert them, I did ask but got no reply even though they were asking for help for something to convert them, I spent a lot of time and looked at a lot of wav to mid apps and put them onto them but then I saw the new Superior Drummer 3 had it so I sent Toontrack a stereo RealDrums file and they tried it and said it worked well with stereo source. It works best with the stems so maybe they used them if the RealDrum had them ?
Not sure if the PG Rock Kit had round robin, if not as you say there are plenty around you can try, just though the PG kit would have the same sound as original tracks.