The source of my rotary knock
 

This has been a long-awaited post (by me); I tore apart the knocking engine I described in this post and have some interesting information to share. I speculated that the rear stat gear bearing failed due to the noise seeming to originate from the rear of the engine, but I was wrong.

Here are some mediocre pictures of the rear rotor & stat gear bearings:

https://cimg3.ibsrv.net/gimg/www.rx8...902146310b.jpg
https://cimg5.ibsrv.net/gimg/www.rx8...e6c645bbc2.jpg
There's no dirt or anything on this rotor bearing, that's pitting and scraping that I assume is from the copper circulating in the oil.

Here is the front stat gear and rotor bearing:
https://cimg2.ibsrv.net/gimg/www.rx8...90a349d929.jpg
https://cimg1.ibsrv.net/gimg/www.rx8...70ef72843a.jpg
I assure you this destroyed bearing is much worse in person than it looks in the picture. I can slide the bearing about half way out of the rotor and it spins freely in there. This rotor is now a decoration.

As you can see, the bearings are all pretty much gone, and the eshaft is probably just as bad as you expected:
https://cimg7.ibsrv.net/gimg/www.rx8...9b5528d39.jpeg

So, there's a lot to do on this motor. I'm curious about something though, the front iron faces and housing aren't destroyed. I thought the knocking noise came from the rotor smacking the mating surfaces. Can anyone confirm or deny this? The only thing I found strange was this sort of uneven wear and burn marks on the front edge of the front housing. I couldn't get great pictures of it, but here they are:
https://cimg2.ibsrv.net/gimg/www.rx8...54ce7eed13.png
https://cimg4.ibsrv.net/gimg/www.rx8...df168794f7.png
Does anybody know what this could be? Maybe that's where it was hitting, but I expected a larger contact area.

That uneven wear was not there when I built this engine, nor was any of that damage to the bearings. I have no idea how this happened. I never ran it low on oil, never revved it cold, changed the oil much more often than necessary, and ran 20w-50. The only questionable thing that I did was use cheap oil filters. I'm not sure, but wondering if that the massive backfire that I described in my original post could have spun this bearing. I had no issues until the car blasted the biggest fireball I've ever heard, and then a bearing was spun. However, I'm also wondering if there's a possibility that the bearing was already spun and it caused that massive backfire that lead me to investigate further, but I highly doubt I wouldn't have noticed the knock. It seemed pretty night and day; no knock prior to backfire, loud knock after backfire.

So, I guess this is a warning for anyone in the future; if you hear what sounds like a knock and can't track it down, I'd recommend you stop driving the car.