I needed to add all four directives above to my answers file to setup nginx and have the install complete successfully. I tried initially to cheat and only add IS_NGINX_SSL, which failed further down the line. I haven't yet tried the red5 setup instructions or done any other post install config.
I ran across the 6 -> 9 upgrade docs while reading some other forum posts, but I haven't given it a try yet. It is more labour intensive, so I ended up weighing how big my DB was vs. how much work it might take. Given that my install is on the smaller side, I thought I'd try a fresh install and then move over the videos that I end up wishing to keep. I plan to keep a copy of my old DB as well, so I can restore to a test box and check the analytics if the need arose.
With the changes you've made with moving to RPMs, the really great thing is that as long as I port over once, I'm good forever thereafter.