Have you looked at the Job Scheduling Board? I think you can do most, if not all of that from there.
I only direct you there because the goal you have for this UBAQ is quite complex, and a simple update query won’t cut it. There are lots of things that happen in the background (BO methods) when you change something in the schedule. It is difficult, even for experienced users, to find all those methods, and reproduce their effect accurately.
Having said all that, if you are bound and determined to learn by fire, start with tracing.
Trace Helper Utility for Epicor ERP 10 - Epicor ERP 10 - Epicor User Help Forum (epiusers.help)
The idea is that you turn on tracing, then perform all the actions you want your UBAQ to do. The trace captures all the BO methods and parameters for you to review. Then just reproduce all that logic perfectly in your UBAQs BPM. Oh yea, you can’t use a basic UBAQ, you will certainly have to use the advanced BPM to create a custom action to tuck all this logic into.
I would try my best to use the canned tools for this one.
Good luck!