Glad to help! This was a learning experience for me as I've been really getting into classic Doom lately and figuring out how to make everything work. It gets pretty confusing. Lots of old formats and info to absorb.
To answer your questions...
1. Yes, those config file entries are correct.
2. To edit the title screen in orig15 I just loaded original.wad in SLADE, exported the title screen file "TITLEPIC", then loaded orig15 and imported that file into it. From there just select the TITLEPIC from the list and on the right there should be some basic manipulation buttons (I just flipped the image). Save orig15 and you're done.
3. DEH files are actually just text files. The music files are listed at the end under all of the "Text"
commands. To explain how that section works, the first of the two numbers is the length of the first string and the second number is the length of the second string. If it finds the first string it replaces it with the second one.
Text 6 6
runnintrack1
This example replaces "runnin" with "track1".
It's used in this case to replace the doom2.wad MIDI filenames with the filenames in original.wad and origig15.wad. But this doesn't apply to libretro PrBoom since the mp3 filenames are apparently hard-coded and it causes a conflict, so we just delete those entries and manually rename the WolfenDoom files to the Doom II filenames it expects with the batch script.
4. Yeah, just put the mp3 files in the same folder as its WAD. I think you do need to put the three WolfenDoom games in separate folders with their own mp3s though since they have some conflicting filenames. (All three in separate subfolders in the Doom II folder)
Also I updated the attachment in my last post. It didn't have the correct filenames for Spear or Nocturnal before but they should work now.
