1) If needed, you could rearrange the export file and make some changes to match the import structure and then import it. But this would add to, not replace, your existing data. This would only be useful if you damaged your account so badly that you wanted to erase all its data and start over. I doubt a bandmate would do that accidentally. If a bandmate makes an accidental change, it is usually easier to roll back the individual changes they made.
2) There is no directory hierarchy for the attached documents and recordings. If you have all the documents in one directory and all the documents in another, you can easily zip those folders and upload them to restore all the documents and recordings. (You might have to break the recordings into a few batches to keep each zip file under the 500 MB upload limit.)
3) If you don't want some fields in the exported file, you can simply open it in Excel or similar and delete those columns. HTML is only used for formatting of lyrics, chords and notes within those fields, not for the overall structure of the file.