I now have the combo unit physically with me and installed in its intended location with initial setup done. I also have the 15-134 remote with some basic functions already entered. I have discovered a lot of new information (from playing around with device and several remotes) about the remote, codes, and devices, but I don't want to get into that yet since it might confuse things.
Please continue with your preferred sequence and I'll do my best to respond with helpful feedback. Refer to the above questions if it helps you understand my mindset.
One thing I would like to mention now- you stated previously that "we know" most of the OBCs and EFCs for the RCA devices and that the numbers are usually repeated across devices and models. If that is the case, then I would simply need the correct programming instructions for approx. 14-18 functions that the stock remote has that are not part of the default universal setup.