<snip> So, my plan is to use BiaB and/or RB to create a decent instrumental demo and then eventually have someone (possibly a female) create a vocal track for me that I could add to the other tracks to finish the demo. Ultimately, I would use the finished demo for various purposes and may even release it as a single or possibly put it on a different album. However, depending on the circumstances, the last two options could justify having it professionally produced, but who I would choose to do that is currently an unknown.
So, I can't really use this song as a basis for answering your other questions.
Instead, I'll use the last song that I recently gave to my producer because it's nearly the same length as this one (317 bars vs. 322 bars). In the past (before I had purchased BiaB), the only file I gave to my producer was a midi file of the melody to my song. Besides the midi file, I also gave him a printout of the lead sheet with all the chords and lyrics along with another printout of a one-page lyric sheet that included the chords. My producer used the lead sheet to perform, arrange, and produce my song, and he used the lyric sheet when he recorded the vocals. For the most recent song with 317 bars that I gave to my producer, I still gave him a midi file, a lead sheet, and a lyric sheet. But I also gave him a single .MP3 file of the audio from BiaB that included drums, a bass guitar, a finger picking acoustic 12-string guitar (left channel), and a 12-string strumming guitar (right channel). In addition, I gave him a .MP4 file of the lead sheet video from MuseScore that had this same audio output from BiaB synced to the melody in the MuseScore video. I used ActivePresenter to create this video and added the audio output from BiaB as a separate track. He imported all three of these files into his DAW, which is Sonar by Cakewalk.
A few weeks after I had given all of the above to my producer, he called me and asked for a new midi file because we had made some last minute changes to the one I had given him that somehow got messed up during his subsequent recording sessions. He also asked me to give him a .MP3 file of just the bass guitar and the finger-picking guitar together and another .MP3 file of the strumming guitar by itself. He didn't need the drums in either of those files because he had already finished recording them. That's the first track he always starts with in his production process. When I gave him these files, he imported them into his DAW to replace the .MP3 file and midi file that I had given him before. However, the three tracks that these audio files occupied in his DAW were only there for him to use as a reference until he had finished recording his own tracks of those same instruments in their place.
"So, I can't really use this song as a basis for answering your other questions." Yes. Your answer works perfectly.
"So, my plan is to use BiaB and/or RB to create a decent instrumental demo..."
Even without a fix for the glitches. BIAB/RB will work perfectly for you. Just not the present way you use them. You can still create your song using MuseScore to make and use an XML file. You can still provide him with a MIDI file, the lead sheet and lyric sheet and a BIAB/RB rendered MP3 file along with the MP4. You can also give him full length individual MP3 tracks of any BIAB/RB generated track such as the bass, fingerpicked guitar and strumming guitar as you did on this recent project. You can do this with any BIAB/RB instrument and including as many tracks as you want.
Regarding your producer requesting changes and edits, you can not only send him a new midi file, but also all of the other tracks your furnished him updated with the edits. You can literally do these type edits in minutes not hours using overdubbing and Punch In/Out techniques and arranging your song in logical sections. Were I doing it, I would generate an audio file for whichever specific section that contains the edit in BIAB and export that audio file and then copy/paste the edited audio to replace the original audio section in RB. The whole file does not have to be regenerated. Either RB or BIAB will crossfade the entry and ending bars into the adjoining original bars seamlessly.