I saved this as an old RCA remote so that the Combo executor would have the EFCs that you're using. See if I understood your notes correctly. BTW, the VCR and DVD setup codes don't actually have Vol+/- or mute. But your remote is setup at the factory to punch through those keys to the TV device. So it seems like DVD and VCR are programmed with Vol, but they're not.
1) When you assign an EFC, the remote stores the device mode, setup code and EFC. The assignment persists even if you change the setup code for that device mode. So you can temporarily put setup code 20522 on the TV button, assign EFCs, and then revert to 10047. So you don't need a spare device button.
2) Do you mean the digital STB wasn't affected until you programmed the SAT button? What setup code did you use? Have you programmed a macro onto the Power button?
3) Happens to me also, but I have no idea why. You can use the Lookup Tool
to find the EFC associated with a key (usually), and then program it that way.