How do I reinstall rekordbox dj without losing my songs with cue points?

If you're going to format, the best way not to lose anything is to go to File > Library > Backup Library and keep the zip file it creates. When you reinstall everything, go to File > Library > Restore Library and point to the zip. It will restore everything, retaining your data.

The only thing you'd need to do is copy your music. If you use the music backup as part of the backup process, it will put them into a weird folder configuration. Don't use that unless you don't mind how they're organized.