It sounds like you have the problem fixed.
Unfortunately, I don't see a way to look at some of the stack fields because they're hidden fields
My fault. You are such an old hand at this stuff I didn't describe how to do that.
Here's something for the future. For hidden fields that don't show up in the drop drown list for adding columns to a View just add using an Expression Column containing just the field name. So an Expression Column containing the expression "[Stack Top]" will show that field.
The conversion setting choices are also a bit unfortunate in this case too. There's no option to leave lower bitrate MP3 files as-is while still converting FLAC and other formats to MP3, so they end up getting converted to higher bitrate MP3's...
If you set the "Handheld Options > "File, Paths, & More > Supported Types" to MP3, and the "Handheld Options > Conversion > Audio > Mode" to "Specified output format only when necessary", then MP3 files shouldn't be converted, but all other files types will be converted.
If the car doesn't support higher bitrate MP3s, let's say it supports 128 bit but nothing higher, then you would set "Handheld Options > Conversion > Audio > Mode" to "Specified output format only when necessary (including high bitrates)" and with the MP3 encoder set to 128 bit MC would convert any higher bitrate MP3 files down to 128, with the caveats as per my notes in the Wiki I linked to earlier.
I tested that functionality last year, and it seemed to all work fine.