What did I do? Help?

Well, if a spare distributor is behaving exactly the same then it can't be in the distributor. I think somehow the distributor drive gear may have came up a little and jumped at least 1 or 2 teeth over then dropped back down when you pulled it the first time. Put it at tdc again and pull the distributor then see where the drive gear slot is clocked. Then hold your distributor in roughly the same position over the hole and see where your rotor is pointing.
I'd be curious to know what your timing reads now if you were to move the pickup clamp to plug wire #8 or #2, or even #4 or #7.
I don't know if that would help verify if the gear could have jumped over or not. Just trying to help but I ain't real smart. It's gotta be something simple though since you didn't have much apart.
edit: My gear was off by a tooth for a while The guy that dynoed my engine installed it that way) and it ran just fine, but when at TDC, the rotor pointed more towards #5 spark plug and I had to rotate the distributor more to get the correct timing, if that makes sense. I moved the gear a tooth and now the rotor points towards plug #1 at TDC again. If you happened to rotate the rotor while pulling the distributor up and out, it could very easily have walked that gear up and over a tooth or two.