Honestly, this all seems overly complex and fragile. I'm not sure what the overall goal is, but if it's to have a general PITR solution, use pgBackRest. If it's just to have a fall back method for a particular change, an easier solution is to stop replication, apply changes, and promote the replica if something goes wrong.
Either way, you should have a test system setup that you can try out your steps on. If a step fails and you do not understand why, this list is a great resource. Practice this a lot on test systems until it all becomes second nature.
