Finally, I've actually made a program that works!!!! Very impressed by how it sounds; pretty much indistinguishable from the original reverb plugin I sampled!
Not sure why it worked this time, probably because I rendered at 32bit and got rid of EA, ER wavs. Anyway for newbies/dumbies, since it isn't spelled out completely anywhere else:
-In an offline mode reverb session, after you've generated the test tone wavs, I believe you're meant to get rid of the EA and ER wavs as they aren't needed here and just keep the large wav. Default name is BackupThis.wav
-Bring that wav into your DAW and render it 100% wet.
-Bounce it as 32-bit wav with the exact same name, and same directory as BackupThis.wav (or whatever you called the generated test tone).
-Deconvolve to create the Nebula program
I'm still confused about the non-existent instructions.txt though. Is that created just for more current sessions, or NAT Platinum or what?