I haven't quite grasped how to handle event conditions in OAUA. Should I use kailung for all of them, just in case, or are there some that are safe to use in the editor? Is it that kailung offers some that aren't available in the editor or are all event conditions available in the editor too but won't work correctly if I don't use kailung to set them?
You must be reading the docs from an earlier version of the OA Worldhack. We did initially have some difficulty with getting ckit to properly handle all of those new event conditions found in OAUA, but all of that was fixed in either version 1.2 or 1.3 of the Worldhack and the documentation notes were updated stating this. As long as you are using the current version of OAUA (and reading those documentation notes), you don't need Kailung.
Kailung, by the way, is the OA version of Brian's Scruadat program. I do still use it occasionally for the same purpose I use Scruadat in my non-OA designs, as a supplement to the UA editor to create event copies, event loops and common text so I can squeeze more out of my dungeons. But it is certainly not required.
And to your other question, yes, I'm afraid the OA Worldhack is as good as it will get now that Brian is gone. Bugs will need to be documented and work arounds discovered. Since I do have several prior versions of the ckit hacks in diff.tbl format, there is still a possibility that I might be able to isolate a specific section of code that is causing problems and revert it back to an earlier version that was working properly, or even do an analysis of the code with a decompiler, but I honestly haven't the time to do such research right now, and it appears only four or five UA'ers (including myself) are even utilizing OAUA at this time. Instead I'm using the scraps of available time I have now trying to finish up Part II of the Tale of Twin Dragons.