< First, why doesn't Band in a Box import the Music XML file correctly in the first place, meaning with a properly notated pick-up measure? >
Your first post comments indicate that BIAB is configured normally in 4/4, 6 note count-in, song begins at bar 1 beat one configuration. BIAB reads whatever data that's included with the Music XML imported file for any re-configuration instructions. It appears to me that while the XML file displays properly in the Music XML program, that program is not exporting the proper data for BIAB to change its configuration to recognize and expect data that BIAB is not configured to see in its current configuration.

< Second, why doesn't the "Nudge Chord/Melody" work as described? >
It's not the proper tool for this task. This seems like a edit copy/paste task.

< Comment 1: I can't get RealBand to do anything but crash whenever I attempt to import any file into it so that option is out, at least for me. >
This also sounds like a configuration issue. Likely between the program and OS. Properly configured, RealBand is stable.
Second, RealBand nor another DAW is necessary to edit a file.

< Comment 2: With all of the "can't do this, can't do that, use a DAW, try this convoluted work around..." issues I have experienced with BiaB in the short time I have used it, I am SO delighted I only bought the Pro Version... >
Valid point. Users are sharing their personal workflow and giving helpful advice from what they've developed to be the easiest and most efficient editing method in regard to their personal knowledge of audio editing. Most have years, if not decades, of use and experience and a highly developed work flow in a DAW environment. It's always good and sufficient advice and instructions in that environment. It also seems a majority of active forum users use a BIAB/DAW combination workflow. While such advice implies BIAB either isn't capable of doing the edit or it's too complex and convoluted to edit in BIAB, that's not the case.

BIAB is a powerful digital Multi Track recorder with a robust Audio Editor and mix capabilities. BIAB can produce a song with dozens of instruments and dozens of tracks in a single song render, just like a DAW. BIAB can effectively bus 4 acoustic guitars, volume leveled and panned on the same track and all getting the same effects on them, just like a DAW. Editing in BIAB is fast, easy, familiar processes that because they're done in BIAB, require no exporting and importing files back and forth between another software program. Editing in BIAB also provides instant review of an edit with all of the other tracks and production of the current BIAB project. Editing in BIAB retains access and availability to all of BIAB's full range of features, tools, techniques and content. No DAW in existence, including RB, can do that.

Your Pro Version purchase delight is misplaced. The core program of BIAB is the same across every version and the 'pro' limitations are in content and accessories only. Your version has all of the powerful recording, editing and mixing capabilities of any level or version of BIAB program. They are all the same.

BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.