Upgrade is already completed, although you will still have to remove the /vault/core/controller/install folder.
For the database error in the front-end during upgrades, there's not much we can do about older versions. In Gamma 1 we added some code that would prevent this from happening in versions after that, but since you started from Beta 5, you did not have access to that code until the entire upgrade process through RC 1 was completed.
Within the upgrade process itself, it seems it wasn't so resilient either when the wiki wasn't upgraded for a lot of versions. I am still trying to find all the spots to avoid this kind of issue for the future.