To be honest I think you need to start again, I'm not going to be able to untangle this. The errors we can see are related to your moving files I expect, but path length is just a red herring. The only path related issue to avoid is starting a folder name with ".", Kodi takes that as hidden and does not scan it.
Start again with your music library.
- Remove the music source,
- Clean the music library (from settings > media > music),
- Ensure that "Fetch additional info on update" is disabled
- Ensure that "Prefer online info" is disabled.
- Add music source and scan to library (this just reads the tags embedded in the music files)
All that should be fine so no debug needed, but feedback if the issue is actually tag scanning related.
Assuming it is scraper (album or artist?) related then turn on debugging.
- Set Universal albums scraper and Universal Artist scraper as the default scarpers
- Go to the albums node, from the context menu choose "query info for all", and let scraping happen (in background but don't do other things).
- If that is succesful go to the artists node, from the context menu choose "query info for all", and again let scraping happen.
If something hangs then please paste a link to the log as the other guys have described.
Warning v17.3 (and below) has a bug in that scraping of Musicbrainz is not correctly throttled, hence the server times out if too many requests are made and the result is missing art and info for even well known artists and albums. But the process should not hang.
But I also have to say why on earth use .rar files for music?
Also the log implies you have cuesheets, is that the case?